Question

(Sin2a/cosa -sina)^2-1 help mee

Answer 1

$( \frac{sin2 \alpha }{cos \alpha }-sin \alpha )^2-1=( \frac{2sin\alpha cos \alpha }{cos \alpha }-sin \alpha )^2-1=( 2sin\alpha-sin \alpha )^2-1=\\ =sin^2 \alpha -1=-cos^2 \alpha$