The expression $\"\"$ and Angle A lies in Quadrant |||.

\

Let $\"\"$ be an angle in standard position with (x, y) a point on the terminal side of $\"\"$ and $\"\"$ .

\

$\"\"$

\

y is negative in Quadrant |||, let $\"\"$ .

\

So, $\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

x is positive in Quadrant |||. So, $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Half angle identities $\"\"$ .

\

Therefore, $\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$