Question

sin2A= (2cotA)/(cot^2A +1)

Answer 1

$= \frac{2cota}{ {cot}^{2} a + 1} \\ = \frac{2cota}{ {cosec}^{2}a } \\ = 2cota \: {sin}^{2} a \\ = 2sinacosa \\ = sin2a$