def construct(self):
formula = TexMobject(*([
"{%d \\over %d} \\cdot" % (wallis_numer(n), wallis_denom(n))
for n in range(1, self.n_terms + 1)
] + ["\\cdots"]))
result = TexMobject("=", "{\\pi \\over 2}")
result.scale(2)
pi = result[-1][0]
pi.set_color(YELLOW)
circle = Circle(color=YELLOW)
circle.surround(pi)
question = TexMobject("?", color=YELLOW)
question.scale(2).next_to(circle, RIGHT, buff=0.4)
result_group = VGroup(result, circle, question)
result_group.next_to(formula, DOWN)
group = VGroup(formula, result_group)
group.center().set_width(10)
bg_rect = BackgroundRectangle(group, fill_opacity=0.5, buff=0.2)
random_walks = VGroup(*[
RandomWalk1DArrow(random_walk_string(30), step_size=0.5)
for k in range(self.n_walks)
])
for k, walk in enumerate(random_walks):
walk.shift(random.randrange(-5, 5) * 2 * walk.step_size * UP)
random_walks.center()
text = TextMobject(self.part).scale(3).set_color(YELLOW)
text.to_corner(RIGHT + DOWN)
self.add(random_walks)
self.add(FullScreenFadeRectangle())
self.add(bg_rect, group, text)
def get_subdivision_braces_and_labels(
self, parts, labels, direction,
buff=SMALL_BUFF,
min_num_quads=1
):
label_mobs = VGroup()
braces = VGroup()
for label, part in zip(labels, parts):
brace = Brace(
part, direction,
min_num_quads=min_num_quads,
buff=buff
)
if isinstance(label, Mobject):
label_mob = label
else:
label_mob = TexMobject(label)
label_mob.scale(self.default_label_scale_val)
label_mob.next_to(brace, direction, buff)
braces.add(brace)
label_mobs.add(label_mob)
parts.braces = braces
parts.labels = label_mobs
parts.label_kwargs = {
"labels": label_mobs.copy(),
"direction": direction,
"buff": buff,
}
return VGroup(parts.braces, parts.labels)
def get_vector_label(self, vector, label,
at_tip=False,
direction="left",
rotate=False,
color=None,
label_scale_factor=VECTOR_LABEL_SCALE_FACTOR):
if not isinstance(label, TexMobject):
if len(label) == 1:
label = "\\vec{\\textbf{%s}}" % label
label = TexMobject(label)
if color is None:
color = vector.get_color()
label.set_color(color)
label.scale(label_scale_factor)
label.add_background_rectangle()
if at_tip:
vect = vector.get_vector()
vect /= np.linalg.norm(vect)
label.next_to(vector.get_end(), vect, buff=SMALL_BUFF)
else:
angle = vector.get_angle()
if not rotate:
label.rotate(-angle, about_point=ORIGIN)
if direction is "left":
label.shift(-label.get_bottom() + 0.1 * UP)
else:
label.shift(-label.get_top() + 0.1 * DOWN)
label.rotate(angle, about_point=ORIGIN)
label.shift((vector.get_end() - vector.get_start()) / 2)
return label
def get_vector_label(self,
vector,
label,
direction="left",
rotate=False,
color=None,
label_scale_factor=VECTOR_LABEL_SCALE_FACTOR):
if not isinstance(label, TexMobject):
if len(label) == 1:
label = "\\vec{\\textbf{%s}}" % label
label = TexMobject(label)
if color is None:
color = vector.get_color()
label.set_color(color)
label.scale(label_scale_factor)
label.add_background_rectangle()
angle = vector.get_angle()
if not rotate:
label.rotate(-angle, about_point=ORIGIN)
if direction is "left":
label.shift(-label.get_bottom() + 0.1 * UP)
else:
label.shift(-label.get_top() + 0.1 * DOWN)
label.rotate(angle, about_point=ORIGIN)
label.shift((vector.get_end() - vector.get_start()) / 2)
return label
def countdown(self):
for k in range(5, -1, -1):
countdown_text = TexMobject(str(k))
countdown_text.scale(1.5)
countdown_text.set_color(YELLOW)
countdown_text.to_corner(RIGHT+UP)
self.add(countdown_text)
self.wait()
self.remove(countdown_text)
def add_brackets(self):
bracket_pair = TexMobject("\\big[ \\big]")
bracket_pair.scale(2)
bracket_pair.stretch_to_fit_height(self.get_height() + 0.5)
l_bracket, r_bracket = bracket_pair.split()
l_bracket.next_to(self, LEFT)
r_bracket.next_to(self, RIGHT)
self.add(l_bracket, r_bracket)
self.brackets = VGroup(l_bracket, r_bracket)
return self
def add_brackets(self):
bracket_pair = TexMobject("\\big[ \\big]")
bracket_pair.scale(2)
bracket_pair.stretch_to_fit_height(self.get_height() + 0.5)
l_bracket, r_bracket = bracket_pair.split()
l_bracket.next_to(self, LEFT)
r_bracket.next_to(self, RIGHT)
self.add(l_bracket, r_bracket)
self.brackets = VGroup(l_bracket, r_bracket)
return self
def construct(self):
wallis_rects_570 = WallisRectangles(order=570)
quarter_circle = Sector(
outer_radius=wallis_rects_570.get_height(),
stroke_color=GREY,
stroke_width=5.70,
fill_opacity=0,
)
quarter_circle.move_arc_center_to(wallis_rects_570.get_bottom_left())
text = TexMobject("n = 570")
text.scale(1.5)
text.move_to(wallis_rects_570.get_top_right())
self.add(wallis_rects_570, quarter_circle, text)
self.wait()
def get_number_mob(self, num):
result = VGroup()
place = 0
max_place = self.max_place
while place < max_place:
digit = TexMobject(str(self.get_place_num(num, place)))
if place >= len(self.digit_place_colors):
self.digit_place_colors += self.digit_place_colors
digit.set_color(self.digit_place_colors[place])
digit.scale(self.num_scale_factor)
digit.next_to(result, LEFT, buff=SMALL_BUFF, aligned_edge=DOWN)
result.add(digit)
place += 1
return result
def get_number_mobjects(self, *numbers, **kwargs):
# TODO, handle decimals
if len(numbers) == 0:
numbers = self.default_numbers_to_display()
if "force_integers" in kwargs and kwargs["force_integers"]:
numbers = list(map(int, numbers))
result = VGroup()
for number in numbers:
mob = TexMobject(str(number))
mob.scale(self.number_scale_val)
mob.next_to(
self.number_to_point(number),
self.label_direction,
self.line_to_number_buff,
)
result.add(mob)
return result
def construct(self):
wallis_rects_5 = WallisRectangles(rect_colors=[
"#FF0000", "#FF8000", "#FFFF00", "#00FF00", "#0080FF"
],
order=5)
quarter_circle = Sector(
outer_radius=wallis_rects_5.get_height(),
stroke_color=GREY,
stroke_width=5.70,
fill_opacity=0,
)
quarter_circle.move_arc_center_to(wallis_rects_5.get_bottom_left())
text = TexMobject("n = 5")
text.scale(1.5)
text.move_to(wallis_rects_5.get_top_right())
self.add(wallis_rects_5, quarter_circle, text)
self.wait()
def solve_the_equations(self):
rects = VGroup(*[
CoverRectangle(
equation[0].get_exponent(), stroke_color = color,
text = str(num), text_color = color
)
for equation, color, num in zip(self.equations, self.colors, self.nums)
])
self.play(DrawBorderThenFill(rects))
self.wait()
sps = VGroup()
for equation, num, color in zip(self.equations, self.nums, self.colors):
sp = TexMobject("x", "^{%d}" % num, "=", "%d" % num)
sp[1::2].set_color(color)
sp.scale(2)
sp.next_to(equation, DOWN, buff = 1)
sps.add(sp)
rss = VGroup()
for num, sp, color in zip(self.nums, sps, self.colors):
rs = TexMobject("x", "=", "%d" % num , "^{{1}\\over{%d}}" % num, "=\\sqrt{2}")
for tex in (rs[2], rs[3][2]):
tex.set_color(color)
rs.match_height(sp).move_to(sp)
rss.add(rs)
tf_anims = []
for sp, rs in zip(sps, rss):
tf_anims.append(ReplacementTransform(sp[0], rs[0]))
tf_anims.append(ReplacementTransform(sp[1], rs[3][2], path_arc = -TAU/4))
tf_anims.append(ReplacementTransform(sp[2], rs[1]))
tf_anims.append(ReplacementTransform(sp[3], rs[2]))
tf_anims.append(Write(rs[3][:2]))
self.play(FadeIn(sps))
self.wait()
self.play(AnimationGroup(*tf_anims), run_time = 2)
self.wait()
self.play(Write(VGroup(*[rs[4:] for rs in rss]), submobject_mode = "all_at_once"))
self.wait()
self.play(FadeOut(rects))
self.wait()
self.rss = rss
def get_det_text(matrix, determinant=None, background_rect=True, initial_scale_factor=2):
parens = TexMobject(["(", ")"])
parens.scale(initial_scale_factor)
parens.stretch_to_fit_height(matrix.get_height())
l_paren, r_paren = parens.split()
l_paren.next_to(matrix, LEFT, buff=0.1)
r_paren.next_to(matrix, RIGHT, buff=0.1)
det = TextMobject("det").next_to(l_paren, LEFT, buff=0.1)
if background_rect:
det.add_background_rectangle()
det_text = VMobject(det, l_paren, r_paren)
if determinant is not None:
eq = TexMobject("=")
eq.next_to(r_paren, RIGHT, buff=0.1)
result = TexMobject(str(determinant))
result.next_to(eq, RIGHT, buff=0.2)
det_text.add(eq, result)
return det_text
def setup(self):
pos_axis = NumberLine(x_min=-4.5, x_max=2.5, color=WHITE)
pos_axis.rotate(np.pi / 2)
pos_axis.add_tip()
time_axis = NumberLine(x_min=0, x_max=9.5, color=WHITE)
time_axis.add_tip()
vec = pos_axis.number_to_point(0) - time_axis.number_to_point(0)
time_axis.shift(vec)
pos_text = TextMobject("位置")
pos_text.next_to(pos_axis.number_to_point(2.5), LEFT)
time_text = TextMobject("时间")
time_text.next_to(time_axis.number_to_point(9.5), DOWN)
axes_group = VGroup(pos_axis, time_axis, pos_text, time_text)
axes_group.center()
title_pq = TexMobject("P_4", "570", "Q_4")
title_pq.scale(1.5)
title_pq.to_corner(UP + RIGHT)
for part, color in zip(title_pq, [ORANGE, BLACK, GREEN]):
part.set_color(color)
r_arrow = TexMobject("\\rightarrow")
l_arrow = TexMobject("\\leftarrow")
for arrow in (r_arrow, l_arrow):
arrow.scale(1.5)
arrow.move_to(title_pq[1])
sequence_p, sequence_q = sequences = ["UDUUDUDD", "DDUDDUDD"]
colors = [ORANGE, GREEN]
walk_p, walk_q = walks = [
RandomWalk1DArrow(sequence, up_color = color, down_color = color) \
.move_start_to(pos_axis.number_to_point(0))
for sequence, color in zip(sequences, colors)
]
parts_p, parts_q = [walk.split_at(3) for walk in walks]
self.axes_group = axes_group
self.title_pq = title_pq
self.walk_p = walk_p
self.walk_q = walk_q
self.parts_p = parts_p
self.parts_q = parts_q
self.r_arrow = r_arrow
self.l_arrow = l_arrow
def get_det_text(matrix, determinant=None, background_rect=True, initial_scale_factor=2):
parens = TexMobject(["(", ")"])
parens.scale(initial_scale_factor)
parens.stretch_to_fit_height(matrix.get_height())
l_paren, r_paren = parens.split()
l_paren.next_to(matrix, LEFT, buff=0.1)
r_paren.next_to(matrix, RIGHT, buff=0.1)
det = TextMobject("det")
det.scale(initial_scale_factor)
det.next_to(l_paren, LEFT, buff=0.1)
if background_rect:
det.add_background_rectangle()
det_text = VMobject(det, l_paren, r_paren)
if determinant is not None:
eq = TexMobject("=")
eq.next_to(r_paren, RIGHT, buff=0.1)
result = TexMobject(str(determinant))
result.next_to(eq, RIGHT, buff=0.2)
det_text.add(eq, result)
return det_text
def reveal_2_is_4(self):
sqrt2_towers = VGroup(*[
ExpTower(element = "\\sqrt{2}", order = 5).match_height(x_tower) \
.move_to(x_tower, aligned_edge = RIGHT)
for x_tower in self.x_towers
])
self.play(
Transform(self.x_towers, sqrt2_towers, submobject_mode = "lagged_start"),
run_time = 2,
)
self.wait()
self.play(FadeOut(self.rss))
self.wait()
two_equals_four = TexMobject("2", "=", "4")
for tex, color in zip(two_equals_four, [GREEN, WHITE, RED]):
tex.set_color(color)
two_equals_four.scale(3)
two_equals_four.to_edge(DOWN, buff = 1)
sources = VGroup(*[
self.equations[i][j][k].copy()
for i, j, k in [(0, 1, 1), (1, 1, 0), (1, 1, 1)]
])
for source, target in zip(sources, two_equals_four):
self.play(Transform(source, target))
self.wait()
fake_qed = FakeQEDSymbol(order = 2, jagged_percentage = 0.3)
fake_qed.next_to(two_equals_four, RIGHT, aligned_edge = DOWN, buff = 1)
self.play(FadeIn(fake_qed))
self.wait()
issue = TextMobject("思考：\\\\问题在哪？")
issue.set_color(YELLOW)
issue.to_corner(RIGHT+DOWN)
self.play(Write(issue), run_time = 1)
self.wait(2)
def add_bars(self, values):
buff = float(self.width) / (2 * len(values) + 1)
bars = VGroup()
for i, value in enumerate(values):
bar = Rectangle(
height=(value / self.max_value) * self.height,
width=buff,
stroke_width=self.bar_stroke_width,
fill_opacity=self.bar_fill_opacity,
)
bar.move_to((2 * i + 1) * buff * RIGHT, DOWN + LEFT)
bars.add(bar)
bars.set_color_by_gradient(*self.bar_colors)
bar_labels = VGroup()
for bar, name in zip(bars, self.bar_names):
label = TexMobject(str(name))
label.scale(self.bar_label_scale_val)
label.next_to(bar, DOWN, SMALL_BUFF)
bar_labels.add(label)
self.add(bars, bar_labels)
self.bars = bars
self.bar_labels = bar_labels
def add_figure(self):
# Main figure
wallis_rects = WallisRectangles(order=10)
order = wallis_rects.get_order()
# Variables and braces on the left
left_rects = [
wallis_rects.get_rectangle(k, 0) for k in [0, 1, 2, 3, -1]
]
left_braces = [
Brace(rect, direction=LEFT, buff=0.1) for rect in left_rects
]
left_lengths = [
TexMobject(symbol)
for symbol in ["a_0", "a_1", "a_2", "a_3", "a_{n-1}"]
]
left_lengths[-1].scale(0.7)
for brace, length in zip(left_braces, left_lengths):
brace.put_at_tip(length, buff=0.15)
left_vdots = TexMobject("\\vdots")
left_vdots.scale(2)
left_vdots.move_to(
(left_braces[-1].get_center() + left_braces[-2].get_center()) / 2)
# Variables and braces on the bottom
down_rects = [
wallis_rects.get_rectangle(0, k) for k in [0, 1, 2, 3, -1]
]
down_braces = [
Brace(rect, direction=DOWN, buff=0.1) for rect in down_rects
]
down_lengths = [
TexMobject(symbol)
for symbol in ["a_0", "a_1", "a_2", "a_3", "a_{n-1}"]
]
down_lengths[-1].scale(0.7)
for brace, length in zip(down_braces, down_lengths):
brace.put_at_tip(length, buff=0.15)
down_cdots = TexMobject("\\cdots")
down_cdots.scale(2)
down_cdots.move_to(
(down_braces[-1].get_center() + down_braces[-2].get_center()) / 2)
# The quarter circle
quarter_circle = Sector(
outer_radius=wallis_rects.get_height(),
stroke_color=GREY,
stroke_width=5.70,
fill_opacity=0,
)
quarter_circle.move_arc_center_to(wallis_rects.get_bottom_left())
# Add everthing
figure_group = VGroup(
wallis_rects,
VGroup(*left_braces),
VGroup(*left_lengths),
left_vdots,
VGroup(*down_braces),
VGroup(*down_lengths),
down_cdots,
quarter_circle,
)
figure_group.center().to_edge(LEFT, buff=0.15)
self.add(figure_group)
def show_the_solution(self):
# Prepare for the solution
pre_solve = VGroup(*self.question[::2])
self.play(
ReplacementTransform(pre_solve, self.solve),
FadeOut(self.question[1]),
run_time = 1,
)
self.wait()
# Manipulate LHS
old_l_part, r_part = self.equation
new_l_part = ExpTower(order = self.highest_order+1, is_infinite = True)
new_l_part.match_height(old_l_part)
new_l_part.next_to(r_part, LEFT, aligned_edge = DOWN)
old_rect, new_rect = rects = [
CoverRectangle(part, text = "2")
for part in (old_l_part, new_l_part.get_exponent())
]
old_two, new_two = twos = [
rect.get_text_mob()
for rect in rects
]
self.play(DrawBorderThenFill(old_rect, run_time = 1))
self.wait()
self.play(
ReplacementTransform(old_l_part, new_l_part),
ReplacementTransform(old_rect, new_rect),
)
self.wait()
new_equation = VGroup(new_l_part, r_part, new_rect)
new_equation.generate_target()
new_equation.target.scale(0.8)
new_equation.target.shift(UP)
self.play(MoveToTarget(new_equation))
self.wait()
# A little bit clean-up
source_eq = VGroup(*[
mob.copy()
for mob in (new_l_part.get_base(), new_two, r_part[0], r_part[1])
])
source_eq.generate_target()
target_eq = TexMobject("x", "^2", "=", "2")
target_eq.scale(3).next_to(source_eq, DOWN, buff = 1)
for k, (old_part, new_part) in enumerate(zip(source_eq.target, target_eq)):
old_part.move_to(new_part)
if k == 1:
old_part.scale(0.5)
old_part.shift(RIGHT/4)
self.play(
FadeOut(new_rect),
MoveToTarget(source_eq),
)
self.wait()
# Reveal the final answer
result = TexMobject("x", "=", "\\sqrt", "2")
result.set_height(source_eq.get_height() * 0.7)
result.move_to(source_eq)
self.play(*[
ReplacementTransform(source_eq[m], result[n], path_arc = angle)
for m, n, angle in [(0, 0, 0), (1, 2, -TAU/3), (2, 1, 0), (3, 3, 0)]
])
self.wait()
qed = QEDSymbol()
qed.next_to(result, RIGHT, aligned_edge = DOWN, buff = 1.5)
self.play(FadeIn(qed))
self.wait()
def construct(self):
colors = ["#FF0000", "#FF8000", "#FFFF00", "#00FF00", "#0080FF"]
wallis_rects_4 = WallisRectangles(
order=5,
rect_colors=colors,
)
vert_lines = VGroup(*[
Line(3.5*UP, 3.5*DOWN, color = GREY, stroke_width = 3) \
.next_to(wallis_rects_4.get_rectangle(0, k), direction, buff = 0)
for k, direction in zip(list(range(5))+[4], [LEFT]*5+[RIGHT])
])
horiz_lines = VGroup(*[
Line(3.5*LEFT, 3.5*RIGHT, color = GREY, stroke_width = 3) \
.next_to(wallis_rects_4.get_rectangle(k, 0), direction, buff = 0)
for k, direction in zip(list(range(5))+[4], [DOWN]*5+[UP])
])
for vert_line in vert_lines:
vert_line.vertically_center()
for horiz_line in horiz_lines:
horiz_line.horizontally_center()
vert_labels = VGroup(*[
TexMobject("a_%d" % k) \
.move_to((vert_lines[k].get_center() + vert_lines[k+1].get_center())/2) \
.shift(3.5*DOWN)
for k in range(5)
])
horiz_labels = VGroup(*[
TexMobject("a_%d" % k) \
.move_to((horiz_lines[k].get_center() + horiz_lines[k+1].get_center())/2) \
.shift(3.5*LEFT)
for k in range(5)
])
area_texs = VGroup()
factors = [1.25, 1, 0.9, 0.7, 0.6]
for p in range(5):
for q in range(5 - p):
rect = wallis_rects_4.get_rectangle(p, q)
tex = TexMobject("{a_%d} {a_%d}" % (q, p))
tex.scale(factors[p + q])
tex.move_to(rect)
area_texs.add(tex)
figure = VGroup()
figure.add(wallis_rects_4, vert_lines, horiz_lines, vert_labels,
horiz_labels, area_texs)
figure.to_edge(LEFT)
self.add(figure)
tex_list = VGroup()
for p in range(5):
formula_string = (
" + ".join(["a_%d a_%d" % (q, p - q)
for q in range(p + 1)]) + "=1")
formula = TexMobject(formula_string)
tex_list.add(formula)
# tex_list.add(TexMobject("\\vdots"))
tex_factors = np.linspace(1, 0.7, 5)
for tex, color, factor in zip(tex_list, colors, tex_factors):
tex.set_color(color)
tex.scale(factor)
tex_list.arrange_submobjects(DOWN, aligned_edge=LEFT)
tex_list.to_edge(RIGHT)
self.add(tex_list)
self.wait()
def construct(self):
# Chart on the left
colors = [WHITE, ORANGE, GREEN]
titles = VGroup(*[
TexMobject(text).set_color(color)
for text, color in zip(["n", "p_n", "q_n"], colors)
])
contents = VGroup(*[
VGroup(*[
TexMobject("%d" % num) for num in
[k, central_binomial_coeff(k),
central_binomial_coeff(k)]
]) for k in range(8)
])
titles.arrange_submobjects(RIGHT, buff=1)
for num, line in enumerate(contents):
for k, element in enumerate(line):
buff = 0.6 + 0.8 * num
element.next_to(titles[k], DOWN, aligned_edge=LEFT, buff=buff)
element.set_color(colors[k])
sep_line = Line(ORIGIN, 4.5 * RIGHT, stroke_width=5)
sep_line.next_to(titles, DOWN)
chart = VGroup(titles, contents, sep_line)
chart.set_height(7)
chart.center().to_edge(LEFT)
self.add(chart)
# Figures on the right
std_zero_pos_axis = NumberLine(x_min=-2,
x_max=2,
color=GREY,
unit_size=0.25,
tick_size=0.05)
std_zero_pos_axis.rotate(np.pi / 2)
std_nocross_pos_axis = NumberLine(x_min=-4,
x_max=4,
color=GREY,
unit_size=0.25,
tick_size=0.05)
std_nocross_pos_axis.rotate(np.pi / 2)
std_time_axis = NumberLine(x_min=0,
x_max=5.5,
color=GREY,
unit_size=0.25,
tick_size=0.05)
std_zero_axes = VGroup(std_zero_pos_axis, std_time_axis)
std_nocross_axes = VGroup(std_nocross_pos_axis, std_time_axis)
zero_walks = VGroup()
for sequence in ["UUDD", "UDUD", "UDDU", "DDUU", "DUDU", "DUUD"]:
axes = std_zero_axes.copy()
zero_walk = RandomWalk1DArrow(sequence, step_size=0.25)
zero_walk.move_start_to(axes[0].number_to_point(0))
zero_walks.add(VGroup(axes, zero_walk))
zero_walks.arrange_submobjects_in_grid(2, 3, buff=0.5)
zero_rect = SurroundingRectangle(zero_walks, color=ORANGE, buff=0.4)
zero_walks.add(zero_rect)
nocross_walks = VGroup()
for sequence in ["DDDD", "DDUD", "DDDU", "UUUU", "UUDU", "UUUD"]:
axes = std_nocross_axes.copy()
nocross_walk = RandomWalk1DArrow(sequence, step_size=0.25)
nocross_walk.move_start_to(axes[0].number_to_point(0))
nocross_walks.add(VGroup(axes, nocross_walk))
nocross_walks.arrange_submobjects_in_grid(2, 3, buff=0.5)
nocross_rect = SurroundingRectangle(nocross_walks,
color=GREEN,
buff=0.4)
nocross_walks.add(nocross_rect)
relation = TexMobject("p_2", "=", "q_2", "=", "6")
relation[0].set_color(ORANGE)
relation[2].set_color(GREEN)
relation.scale(1.5)
figure = VGroup(zero_walks, relation, nocross_walks)
figure.arrange_submobjects(DOWN)
figure.set_height(7)
figure.center().to_edge(RIGHT)
self.add(figure)
self.wait()
def generate_points(self):
dots = TexMobject(*list("..."))
dots.arrange_submobjects(RIGHT, buff = self.gap_buff)
dots.rotate(self.angle)
dots.scale(1.5)
self.add(dots)
