def lawOfCosines(sideA, sideB, sideC):
# solves for the ANGLE given the three side lengths
# this corresponds to the pixel lengths that we're already getting
# from teh star camera
# first compute the thing going into acos
arg = sideA**2 + sideB**2 - sideC**2
arg = arg/(2*sideA*sideB)
angle = ST.acosd(arg)
return angle
