Question

prove it fast it so nice question

Answer 1

Given : SinA + sin3A/cosA + cos3A

$Note : sin A + sin B = 2 sin \frac{A + B}{2} cos \frac{A - B}{2}$

$Note : cos A + cos B = 2 cos \frac{A + B}{2} cos \frac{A - B}{2}$

Now,

$\frac{2 sin \frac{3A + A}{2} cos \frac{3A - A}{2} }{2 cos \frac{3A + A}{2} cos \frac{3A - A}{2} }$

$\frac{2 sin 2A cos A}{2 cos 2A cosA}$

$\frac{2sin2A}{2cos2A}$

$\frac{sin2A}{cos2A}$

tan 2A.


Hope this helps!

Answer 2

Hi,

Please see the attached file!


Thanks