Below is an *inverse cosine calculator* (or *arccos calculator*), which calculates an angle from the ratio from the cosine function. Enter the result and choose to return radians or degrees, then compute the angle.

## Inverse Cosine Calculator

**Table of Contents**show ▼

## Using the Arccosine Calculator

To use the tool to find the angle from a cosine, enter the ratio, choose the units you'd like as output, and compute.

**Cosine**- ratio of the adjacent side over the hypotenuse**Output Degrees or Radians?**- choose to return degrees or radians

Once you're happy, click the "Compute Arccos" button.

**Angle**- the angle you'd input if you wanted to get the cosine you entered

## What is the arccosine or inverse cosine?

Arccosine is the inverse of the cosine, which is the ratio of the adjacent side over the hypotenuse (longest side) in a right triangle.

The adjacent side can never be larger than the hypotenuse as it can at most match the length. This means arcsine can only be between -1 and 1.

### Arccosine as a formula

Inverse cosine is usually abbreviated as "arccos" or "acos", as in the following equation:

arccos(y) = acos(y)

Where it is the inverse of cosine, or:

x=arccos(y)\\y=cos(x)

*Next, see all the inverse trigonometric functions* or

*trigonometric functions in one tool.*