Question

the law of cosines can be applied to right triangles

Answer 1

Yes it does get applied; http://mathworld.wolfram.com/LawofCosines.html

Answer 2

if we apply the law of cosines to the hypotenuse of a right-angled triangle
we get

c^2 = a^2 + b^2 - 2ab cos 90

now since cos 90 degrees = 0

c^2 = a^2 + b^2 - Pythagoras!!!

Answer 3

thnx