Angle between two lines is wrong

Question

I want to get angles between two line. So I used this code.

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int posX = (ScreenWidth) >> 1;

int posY = (ScreenHeight) >> 1;

double radians, de         


        

Answer 1

Here's a function I use. It works great for me...

float cartesianAngle(float x, float y) {
    float a = atanf(y / (x ? x : 0.0000001));
    if      (x > 0 && y > 0) a += 0;
    else if (x < 0 && y > 0) a += M_PI;
    else if (x < 0 && y < 0) a += M_PI;
    else if (x > 0 && y < 0) a += M_PI * 2;
    return a;
}

EDIT: After some research I found out you can just use atan2(y,x). Most compiler libraries have this function. You can ignore my function above.