Question

Sin a /1+cos a = 1-cos a /sin a

Answer 1

$\frac{ \sin(a ) }{1 + \cos(a) } \times \frac{1 - \cos(a) }{1 - \cos(a ) } = \frac{ \sin(a(1 - \cos(a) ) }{ {1 }^{2} - \ { \cos(a) }^{2} } \\ \frac{ \sin(a)(1 - \cos(a) ) }{ { \sin(a) }^{2} } = \frac{1 - \cos(a) }{ \sin(a ) } \\ hence \: proved$