The inverses of the trigonometric functions
(x = sin(y), x = cos(y), etc.) aren't
functions, they are
relations. The reason they are not functions
is that for a given value of x, there are an infinite number of angles at
which the trigonometric functions take on the value of x. Thus, the range
of the inverses of the trigonometric functions must be restricted to make them
functions. Without these restricted ranges, they are known as the inverse
trigonometric relations.

The six inverse trigonometric functions are arcsine, arccosine,
arctangent, arccosecant, arcsecant, and arccotangent. Sometimes
they are capitalized to differentiate them from the inverse trigonometric
relations. In this text, they will not be capitalized; the distinction will be
made clear another way. x = sin(y) is equivalent to y = arcsin(x). This
is the way that all of the inverse trigonometric functions are
defined. In the chart below are shown the
domains and ranges of the inverse trigonometric
functions.

Below are pictured the graphs of the six inverse trigonometric relations. Study
the restricted ranges that turn these relations into functions, and then locate
the sections of the graphs of the relations that become the graphs of the
functions. Verify that they are indeed functions.

The inverse trigonometric functions are useful in solving wide varieties of
trigonometric functions. On calculators, they appear as sin^{-1}, cos^{-1}, tan^{-1}, etc. This symbolism for the inverse of the functions should not be
confused with negative exponents.