posted by McKenna Louise on .
Using the Law of Cosines, how can I show that the measure of each angle of an equilateral triangle is 60 degrees?
since the sides are all equal,
s^2 = s^2+s^2 - 2s^2 cosθ
cosθ = 1/2
since you can pick any side, the value for θ is good for all three angles.