# ACOS

## Purpose:

Calculates the inverse cosine of any expression.

## Syntax:

ACOS(val)

 val - A scalar, series or table.

## Returns:

A scalar, series, or table.

## Example:

acos(-1..0.01..1);gridhv;griddot

displays the inverse cosine from –1 to 1.

## Example:

acos(0)

returns 1.570796 or π/2.

## Example:

acos(-2..0.1..2)

returns a 41 point complex series.

## Remarks:

The inverse cosine is defined as:

for all complex z. The function is multi-valued and this definition places the branch cut in the complex plane at [-∞, -1] and [1, ∞].

For |x| > 1, acos(x) returns a complex result.

The function calculates in radians unless degrees are specified with the SETDEGREE function.

ACOSH

ASEC

ASIN

COS

COSH

GACOS

SETDEGREE