Triangles - finding angles between lines.

triangles.c

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

//c99 removed M_PI, so check if it's defined, if not, define it
#ifndef M_PI
#define M_PI acos(-1.0) 
#endif

void triangles(double a, double b, double h){
    assert(a>0 && b>0 && h>0);
    printf("This is wrong, but the calculated angle between side a and side b is %.2f, even though we know it should be 90.\n", atan(a/b)*180.0/M_PI);
    printf("The angle between side b and side h is %.2f\n", acos(b/h)*180.0/M_PI);
    printf("The angle between side a and side h is %.2f\n", acos(a/h)*180.0/M_PI);
}

int main(){
    triangles(3,4,5);
    return 0;
}