Question

sum of compound angles... help me to do it​

Answer 1

$70 - 20 = 50$

$\tan(70 - 20) = \tan(50)$

$\frac{ \tan70 - \tan(20) } {1 + \tan(70) \tan(20) } = \tan(50)$

$\frac{ \tan(70) - \tan(20) }{1 + 1} = \tan(50)$

$\tan(70) - \tan(20) = 2 \tan(50)$