How to keep the direction of line unchanged in the recursion?

Question

With this function I want to draw a recursive tree but, when I call this function the direction of second line (which I want to draw recursively changes each time).

a Is the angle between x and the first line,

b Is the angle between first line and second line.

Photos: This is the First level recursion This is the second level of recursion the problem is at highlighted line How can I fix this problem?

public void drawTree(int n, float l, float x, float y, float a, float b, float c, 
                     float k1, float k2, float k3, float m2, float m3)
{
    //float k = (float)Math.Pow(-1, n+1);
    Pen p = new Pen(Color.Black);
    Graphics gr = this.CreateGraphics();

    float l1 = k1 * l;
    float l2 = k2 * l;
    float l3 = k3 * l;
    float g = m3 * l;
    float f = m2 * l;

    gr.DrawLine(p, x, y, x + l * cos(a), y - l * sin(a));
    if (n == 1) return;

    drawTree(n - 1, l2, x + f * cos(a), y - f * sin(a), (a - b), b, c, k1, k2, k3, m2, m3);
}

Answer 1

Every time you compute the new point, you're subtracting it from y which if sin(a) was positive, would be fine, but since it's not, it flips from being a negative subtraction to a positive subtraction.

If you iterate one level deeper, the next line should be drawn correctly.

Try either using a positive value a or Math.Abs the resulting sin(a) .