1. ## Finding Angles(Factor Formulae)

Find all angles between 0 and $\displaystyle \pi$ for which $\displaystyle 4cos\frac{A}{2}cosAsin\frac{5A}{2}=0$

2. Hello Punch
Originally Posted by Punch
Find all angles between 0 and $\displaystyle \pi$ for which $\displaystyle 4cos\frac{A}{2}cosAsin\frac{5A}{2}=0$
Given that
$\displaystyle 4\cos\frac{A}{2}\cos A\sin\frac{5A}{2}=0$
any of these three factors could be zero. So you must solve:
$\displaystyle \cos\frac{A}{2}=0$
and
$\displaystyle \cos A=0$
and
$\displaystyle \sin\frac{5A}{2}=0$
Can you do that?

Hello PunchGiven that
$\displaystyle 4\cos\frac{A}{2}\cos A\sin\frac{5A}{2}=0$
any of these three factors could be zero. So you must solve:
$\displaystyle \cos\frac{A}{2}=0$
and
$\displaystyle \cos A=0$
and
$\displaystyle \sin\frac{5A}{2}=0$
Can you do that?

4. Just a little question if $\displaystyle \sin\frac{5A}{2}=0$, then in what quadrants does A lies in? Does zero means that it is positive or negative?