The trigonometric expression is .

Coterminal angle .

where is any negative or positive integer.

Substitute and in .

is cooresponds to the point   on the unit circle.

Trigonometric function : .

.

Take the angle .

is cooresponds to the point on the unit circle.

Trigonometric function : .

.

.

Take the angle .

is cooresponds to the point on the unit circle.

Trigonometric function : .

.

or .

or .