Question

2sinA/1-sin(n/2-2A) = ctgA

Answer 1

$\frac{sin2a}{1-sin( \frac{\pi}{2}-2a) }=ctga \\ \frac{2sinacosa}{1-cos2a}= \frac{2sinacosa}{sin^{2}a+cos^{2}a-cos^{2}a+sin^{2}a}= \frac{2sinacosa}{2sin^{2}a}= \frac{2cosa}{2sina}= \frac{cosa}{sina}=ctga$