How to use Pi number=3.14. in C language?

Question

i have to calculate this number.
r2 = 122 + 52
r = √ (122 + 52)
r = √ (144 + 25)
r = √ (169) = 13

Answer 1

Check out the comments here:
https://www.sololearn.com/learn/6136/?ref=app

Answer 2

#define PI 3.14

or:
#define _USE_MATH_DEFINES
#include <math.h>
/*
* M_PI = pi
* M_PI_2 = pi/2
* M_PI_4 = pi/4
* M_1_PI = 1/pi
* M_2_PI = 2/pi
* M_2_SQRTPI = 2/sqrt(pi)
*/

Answer 3

@Jan Markus i updates question see.

Answer 4

https://www.sololearn.com/discuss/1204085/?ref=app

Answer 5

@thanx alex