# ACos

## Summary

Calculates the inverse cosine of cells in a raster.

## Usage

• In mathematics, all Trigonometric functions have a defined range of valid input values, called the domain. The output values from each function also has a defined range. For this tool

• The Domain is : -1 ≤ [in_value] ≤ 1

Note that any input value that is outside this domain will receive NoData on the output raster.

• The Range is : 0 ≤ [out_value] ≤ pi

• The input values to this tool are interpreted as unitless.

• Output values are always floating point, regardless of the input data type.

• The output values from this tool are in radians. If degrees are desired, the resulting raster must be multiplied by the radians-to-degrees conversion factor of 180/pi, or approximately 57.296.

For further assistance, a procedure to follow and some examples of converting output in radians to degrees are available.

• See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

## Syntax

`ACos (in_raster_or_constant)`
 Parameter Explanation Data Type in_raster_or_constant The input for which to calculate the inverse cosine values.In order to use a number as an input for this parameter, the cell size and extent must first be set in the environment. Raster Layer; Constant

#### Return Value

 Name Explanation Data Type out_raster The output raster.The values are the inverse cosine of the input values. Raster

## Code sample

ACos example 1 (Python window)

This example calculates the inverse cosine of the values in the input Grid raster and outputs a TIFF raster.

``````import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outACos = ACos("degs")
outACos.save("C:/sapyexamples/output/outacos.tif")``````
ACos example 2 (stand-alone script)

This example calculates the inverse cosine of the values in the input Grid raster.

``````# Name: ACos_Ex_02.py
# Description: Calculates the inverse cosine of cells in a raster
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inRaster = "degs"

# Execute ACos
outACos = ACos(inRaster)

# Save the output
outACos.save("C:/sapyexamples/output/outacos")``````

## Licensing information

• ArcGIS Desktop Basic: Requires Spatial Analyst or Image Analyst
• ArcGIS Desktop Standard: Requires Spatial Analyst or Image Analyst
• ArcGIS Desktop Advanced: Requires Spatial Analyst or Image Analyst