### ACOS(number)

Returns the arc-cosine of a number.

 number The number you want the arccosine of.

#### Remarks

* The arc-cosine of an angle is the inverse of the COS function.
* The "number" is the cosine of an angle in radians.
* If "number" is not numeric, then #VALUE! is returned.
* The angle returned is in radians between 0 and PI.
* If your argument is in degrees, multiply it by PI/180 to convert it to radians.
* If your argument is in radians, multiply it by 180/PI to convert it to degrees.
* If you want to convert the result from radians to degrees, multiply it by 180/PI.
* You can use the DEGREES function to convert from radians to degrees.
* For a working example refer to Trigonometry page.
* For the Microsoft documentation refer to support.office.com.

 A 1 =ACOS(0.5) = 1.047 2 =ACOS(-1) = 3.142 3 =ACOS(1) = 0 4 =ACOS(COS(1)) = 1 5 =ACOS(COS(0.5)) = 0.5 6 =ACOS(-0.5)*180/PI() = 120 7 =ACOS(-1)*180/PI() = 180 8 =DEGREES(ACOS(-1)) = 180 9 =ACOS(DEGREES(-0.5)*PI()/180)*180/PI() = 120 10 =ACOS(10) = #NUM! 11 =ACOS("some text") = #VALUE!

#### Expand ...

1 - What is the arc-cosine of 0.5 radians.
2 - What is the arc-cosine of -1 radians.
3 - What is the arc-cosine of 1 radian.
4 - This function is the inverse of the cosine function.
5 - This function is the inverse of the cosine function.
6 - How many degrees is the arc-cosine of -0.5 radians.
7 - How many degress is the arc-cosine of -1 radians.