# acos - Returns the value of cosine in C

acos - Returns the value of cosine
Explanation: Acos is used to find the arccosine of a number (give it a cosine value and it will return the angle, in radians corresponding to that value). It must be passed an argument between -1 and 1.

Syntax:
acos(int value);

```  #include <math.h>
#include <stdio.h>

int main(void)
{
double val = -1.0;

do {
printf("Arc cosine of %f is %f.\n", val, acos(val));
val += 0.1;
} while(val<=1.0);

return 0;
}
```

Output:
Arc cosine of -1.000000 is 3.141593.
Arc cosine of -0.900000 is 2.690566.
Arc cosine of -0.800000 is 2.498092.
Arc cosine of -0.700000 is 2.346194.
Arc cosine of -0.600000 is 2.214297.
Arc cosine of -0.500000 is 2.094395.
Arc cosine of -0.400000 is 1.982313.
Arc cosine of -0.300000 is 1.875489.
Arc cosine of -0.200000 is 1.772154.
Arc cosine of -0.100000 is 1.670964.
Arc cosine of -0.000000 is 1.570796.
Arc cosine of 0.100000 is 1.470629.
Arc cosine of 0.200000 is 1.369438.
Arc cosine of 0.300000 is 1.266104.
Arc cosine of 0.400000 is 1.159279.
Arc cosine of 0.500000 is 1.047198.
Arc cosine of 0.600000 is 0.927295.
Arc cosine of 0.700000 is 0.795399.
Arc cosine of 0.800000 is 0.643501.
Arc cosine of 0.900000 is 0.451027.
Arc cosine of 1.000000 is 0.000000.