Question

how sin2a +cos2a =1

Answer 1

what is the question must u prove that the RHS=LHS?

Answer 2

prove that this question?

Answer 3

you mean sin^2 a + cos^2 a = 1.

Answer 4

What I do is remember how sin and cos can be thought of as coming out of the unit sphere, with certain angles, and forming a right angle triangle from the angle, etc. Then you just have pythagoras' theorem.