The expression is $\"\"$ \ \

$\"\"$

Even odd identities : $\"\"$

$\"\"$ \ \

Since $\"\"$

$\"\"$

The function $\"\"$ has a period of $\"\"$ , first find all solutions in the interval $\"\"$ .

The function $\"\"$ is positive in first and second quadrant. \ \

The first quadrant : \ \

$\"\"$

Second quadrant : \ \

$\"\"$

$\"\"$ has solutions $\"\"$ in the interval $\"\"$ .