Solving Trigonometric Equations
Concept

Inverse Trigonometric Functions

The inverse trigonometric functions are the inverse functions of the trigonometric functions. For example, the inverse sine is the inverse function of the sine function. The main inverse trigonometric functions are shown in the table below.
Trigonometric Function Inverse Trigonometric Function
f(x)=sinx f^(-1)(x)=sin^(-1)x
f(x)=cosx f^(-1)(x)=cos^(-1)x
f(x)=tanx f^(-1)(x)=tan^(-1)x
The inverse trigonometric functions relate an input, which represents the ratio of two sides of a right triangle, to the measure of one of its two acute angles. The output angles are measured in radians.
Unit Circle Inverse Trigonometric Ratios
The domain of the corresponding trigonometric function must be restricted in order for its inverse to be defined as a function.
The domain of the basic trigonometric functions being restricted and then the inverse is graphed
The properties of the main inverse trigonometric functions are summarized in the following table.
Inverse Trigonometric Function Domain Range
y=sin^(-1)x [-1,1] -π/2 ≤ x ≤ π/2
y=cos^(-1)x [-1,1] 0≤ x ≤ π
y=tan^(-1)x All real numbers -π/2 ≤ x ≤ π/2

Note that the inverse trigonometric functions sin^(- 1) x, cos^(- 1) x, tan^(- 1) x are also called arcsinx, arccosx, and arctanx, respectively. These can also be written as Arcsin x, Arccos x, and Arctan x, respectively.

Exercises