# ACOS

The `ACOS` function returns the arccosine of a value, which is the angle in radians whose cosine is the specified value. The function is often used in trigonometry to find the angle of a right triangle given the adjacent and hypotenuse. The value parameter must be a number between -1 and 1.

## Usage

Use the `ACOS` formula with the syntax shown below, it has 1 required parameter:

Parameters:
1. value (required):
The value whose arccosine is to be returned. Must be a number between -1 and 1.

## Examples

Here are a few example use cases that explain how to use the `ACOS` formula in Google Sheets.

### Find the angle of a right triangle

Given the length of the adjacent and hypotenuse of a right triangle, you can use the `ACOS` function to find the angle opposite to the adjacent side.

### Calculate the inverse cosine of a value

The `ACOS` function is used to calculate the arccosine of a given value, which is the angle whose cosine is that value.

### Calculate the angle between two vectors

The `ACOS` function can be used to find the angle between two vectors in three-dimensional space.

## Common Mistakes

`ACOS` not working? Here are some common mistakes people make when using the `ACOS` Google Sheets Formula:

### Invalid argument type

The ACOS formula requires a numeric value as input. If the input is not a number, the formula will return an error. To fix this, make sure the input is a valid number.

### Out of range input

The input value for ACOS must be between -1 and 1. If the input is outside this range, the formula will return an error. To fix this, make sure the input is within the valid range.

### Incorrect syntax

The ACOS formula requires one input value. If there are too many or too few arguments, the formula will return an error. To fix this, check the syntax of the formula and make sure it has the correct number of arguments.

The following functions are similar to `ACOS` or are often used with it in a formula:

• `SIN`

The `SIN` function in Google Sheets returns the sine of a given angle in radians. Sine is a mathematical function that describes a smooth repetitive oscillation. It is commonly used in trigonometry, physics, and engineering to model phenomena such as waves, oscillations, and periodic motion.

• `COS`

The `COS` function in Google Sheets returns the cosine of an angle provided in radians. It is commonly used in trigonometry to calculate the cosine of an angle. The function takes one parameter, the angle in radians.

• `TAN`

The `TAN` function returns the tangent of an angle specified in radians. Tangent is the ratio of the length of the opposite side to the length of the adjacent side of a right-angled triangle. This function is commonly used in trigonometry and geometry calculations.

You can learn more about the `ACOS` Google Sheets function on Google Support.