To find the arccosine, or inverse cosine, of a number, we can use the php acos() function.


In php, we can easily use trigonometric functions from the collection of php math functions. These php math functions allow us to perform trigonometry easily.

To find the arccosine of a number, we use the php acos() function.

Below is the php syntax to find the inverse cosine of a number.


The input to the acos() function must be a float between -1 and 1. The return value will be a float between 0 and pi radians.

echo acos(0.5); // 1.0471975511965979
echo acos(0); // 1.5707963267948966
echo acos(-0.75); // 2.4188584057763776

Finding the Inverse Cosine of a Number in php

Arccosine is defined as the inverse of the cosine of a number.

Below, we show that if we pass a number to cos() and then call the php acos() function, we get back the same number.

echo acos(cos(pi()/3)); // 1.0471975511965976
echo pi()/3; // 1.0471975511965976

Hopefully this article has been beneficial for you to understand how to use the acos() function in php to find the arccosine of a number.

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Last Update: February 26, 2024