Asked by liger

prove:
sinx/sec2x+cosx/csc2x=sin3x
Answered by Reiny
LS = sinx(cos2x) + cosx(sin 2x)

RS = sin(3x) = sin(2x + x)
= (sin 2x)cosx + (cos 2x) sinx
= LS

I am using sin(A+B) = sinAcosB + cosAsinB