#define M_E         2.71828182845904523536028747135266250   /* e */
#define M_LOG2E     1.44269504088896340735992468100189214   /* log 2e */
#define M_LOG10E    0.434294481903251827651128918916605082  /* log 10e */
#define M_LN2       0.693147180559945309417232121458176568  /* log e2 */
#define M_LN10      2.30258509299404568401799145468436421   /* log e10 */
#define M_PI        3.14159265358979323846264338327950288   /* pi */
#define M_PI_2      1.57079632679489661923132169163975144   /* pi/2 */
#define M_PI_4      0.785398163397448309615660845819875721  /* pi/4 */
#define M_1_PI      0.318309886183790671537767526745028724  /* 1/pi */
#define M_2_PI      0.636619772367581343075535053490057448  /* 2/pi */
#define M_2_SQRTPI  1.12837916709551257389615890312154517   /* 2/sqrt(pi) */
#define M_SQRT2     1.41421356237309504880168872420969808   /* sqrt(2) */
#define M_SQRT1_2   0.707106781186547524400844362104849039  /* 1/sqrt(2) */

#include <math.h>
#include <iostream>
using namespace std;
double cosd(double i)
{
        return cos(M_PI*i/180);
}
int main()
{
        // smá dæmi um þríhyrning
        double adlaegskamhlid = 3;
        double langhlid = 5;
        double horn = acos(adlaegskamhlid/langhlid);
        double motlskamhlid = langhlid*sin(horn);
        cout << "cos af  pí/4: " << cos(M_PI/4) << endl;
        cout << "cos af 60 gráðum: " << cosd(60) << endl;
        cout << "thrihirningur: " << endl;
        cout << "horn: " << horn << " radianar" << endl;
        cout << "motlaegskamhlið: " << motlskamhlid << endl;
        return 0;
}