Here's the question you clicked on:
sunnymony
how sin2a +cos2a =1
what is the question must u prove that the RHS=LHS?
prove that this question?
you mean sin^2 a + cos^2 a = 1.
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.
|dw:1353754710511:dw|
you can actually prove it on any right-angled triangle by drawing it as follows: |dw:1353754910236:dw|
then use definition of sin(theta) and cos(theta) and pythagorus to prove it