Get vC where vA.Y == vB.Y

public static Vector2 GetC(Vector2 vA, Vector2 vB, double angleC)
{
    //   vA - - - vD - - - vB
    //    \        |       /
    //     \       |      /
    //      \      |     /
    //       \     |    /
    //        \    |   /
    //         \   |  /
    //          \  | /
    //            \|/
    //            vC

    double angleA = 180 - angleC - 90;
    Vector2 vD = (vA + vB)/2;
    double lengthAD = (vA - vB).Length();
    double lengthCD = lengthAD * Math.Cos(angleA);

    // Solve for m
    double m = lengthCD / lengthAD;

    // Solve for b
    double b = vA.Y - m * vA.X;

    Vector2 vC = new Vector2(vD.X, (float)m * vD.X + (float)b);

    return vC;
}