$\"\"$

Observe the diagram.

The length of opposite side to $\"\"$ is $\"\"$ .

The length of adjacent side to $\"\"$ is $\"\"$ .

Trigonometric function : $\"\"$ .

$\"\"$

Defnition of inverse tangent : $\"\"$ if and only if $\"\"$ .

$\"\"$

$\"\"$ .

The angle $\"\"$ is $\"\"$ .

$\"\"$

The angle $\"\"$ is $\"\"$ .