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c++type-conversioncmathtrigonometry

problems with cMath and the sin function

Hey so i'm doing some graphics math and inserting what i believe to be a float (i'm pretty sure the ways i manipulate the float beforehand is messing something up somehow...) into the function and getting strange, negative results back.

for instance when doing the following opperations when Angle initially equals 350.0, test ends up being
-.99. Why?

Angle= (float)(Angle-(int)Angle)+(float)((int)Angle%90); 

// calculates x and y based on angle and Hypotenuse
float test= sin(Angle);
float test2= 1/(Speed*Time);
float test3= test/test2;
buffX= sin(Angle)/ (1.f/(Speed*Time));
buffY= sin(Angle-90)/ (1.f/(Speed*Time));

trying to keep Angle a float by putting (float) before everything didn't work... please help! Thanks!

Solution

  • That's because the C/C++ runtime function sin() expects the argument in radians, not degrees.

    Convert to radians with:

    float test= sin(Angle / 180 * M_PI);

    etc.