Question

1. Prove the following
7.
sin (A+B)
=tan A + tan B
cos A.cos B​

Answer 1

Answer:

$\frac{ \sin(a + b) }{ \cos(a) \cos(b) } = \frac{ \sin(a) \cos(b) + \cos(a) \sin(b) }{ \cos(a) \cos(b) } = \frac{ \sin(a) \cos(b) }{ \cos(a) \cos(b) } + \frac{ \cos(a) \sin(b) }{ \cos(a) \cos(b) } = \frac{ \sin(a) }{ \cos(a) } + \frac{ \sin(b) }{ \cos(b) } = \tan(a) + \tan(b)$