$\"\"$

\

The angle is $\"\"$ .

\

Coterminal angle $\"\"$ .

\

where $\"\"$ is any negative or positive integer.

\

Substitute $\"\"$ and $\"\"$ in $\"\"$ .

\

A coterminal angle is $\"\"$ .

\

The terminal side of $\"\"$ lies in Quadrant I.

\

Therefore, its reference angle is $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Reference angle is $\"\"$ .

\

$\"\"$