Trigonometric functions

There are six trigonometric functions corresponding to the six trigonometric ratios. Because of their periodic nature, trigonometric functions are not invertible (not over their entire domain); i.e. they do not pass the horizontal line test. Inverse trigonometric functions are obtained only by restricting the domain/range of trigonometric functions.

The length of the red segment is equivalent to the cosine of the angle, while that of the blue segment to the sine of the angle.

The length of the red segment is equivalent to the cotangent of the angle, while that of the blue segment to the tangent of the angle.

The length of the red segment is equivalent to the secant of the angle, while that of the blue segment to the cosecant of the angle.