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The ** cos() function** returns the cosine of a number. To be more specific, it returns the cosine of a number in the radian float value.

Figure 1 shows the mathematical representation of the `cos()`

function.

Note:

- The
`math.h`

header file is required for this function.- This
`cos()`

function only works for right-angled triangles.

```
double cos(double num)
```

This function requires a `number`

that represents an `angle`

in `radians`

as a parameter.

In order to convert `degrees`

to `radians`

, use the following formula:

```
radians = degrees * ( PI / 180.0 )
```

`cos()`

returns the `cosine`

of a number `(radians float value)`

that is sent as a parameter.

#include<stdio.h> //header file #include<math.h> int main() { //positive number in radians printf("The cosine of %lf is %lf \n", 2.3, cos(2.3)); // negative number in radians printf("The cosine of %lf is %lf \n", -2.3, cos(-2.3)); //converting the degrees angle into radians and then applying cos() // degrees = 90.0 // PI = 3.14159265 // result first converts degrees to radians then apply cos double result=cos(90.0 * (3.14159265 / 180.0)); printf("The cosine of %lf is %lf \n", 90.0, result); }

RELATED TAGS

c

math

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