Converting Between Degrees and Radians

In order to convert degrees to radians, multiply the angle in degrees by $\pi$ and divide by $180\degree$:

$$45\degree = 45\degree \times \frac{\pi}{180\degree} \ =\frac{\pi}{4} $$

Take for example the code:

#include <math.h>
#include <stdio.h>
#define PI acos(-1.0)

void clear_input_buffer() {
  int ch;
  while ((ch = getchar()) != '\n' && ch != EOF)
    ;
}

int main() {

  float angle_in_degrees;
  int correct_inputs = 0;

  do {
    printf("Please enter an angle in degrees to convert to radians:\n");
    correct_inputs = scanf("%f", &angle_in_degrees);
    if (correct_inputs == 0) {
      printf("Invalid input\n");
    }
    clear_input_buffer();
  } while (correct_inputs == 0);

  printf("The angle in radians is %f\n", PI * angle_in_degrees / 180.0);
  return 0;
}

Conversely, we can convert from radians back to degrees by multiplying by $180\degree$ and dividing by $\pi$: $$\frac{\pi}{3}=\frac{\pi}{3}\times \frac{180\degree}{\pi}=60\degree$$

Challenge

Convert the following angles to radians:

• $45\degree$
• $360\degree$
• $-135\degree$

Convert the following angles to degrees:

• $\frac{\pi}{4}\ rad$
• $3\pi \ rad$
• $\frac{-\pi}{5}\ rad$

Rewrite the C code above to convert an angle in radians, provided by the user, back to degrees.