angleTo

Line angleTo Line => Angle
Returns the signed angle turning this line's direction onto other's — counter-clockwise positive, in (−π, π].

The cosine is the lines' weight contraction a ∨ b^☆ and the sine the raw weight of their crossing point a ∨ b — for unit normals (gx, gy), the normals' dot and cross products — combined by atan2, so the answer is well-behaved at every angle. The result is raw at full Double precision. Equal directions answer the zero angle, and reversing either line's orientation offsets the answer by a half turn; the unoriented angle between the carriers is min(|φ|, π − |φ|). A line at infinity — zero normal — has no direction, and the answer degenerates to the zero angle; gate with Line.isAtInfinity.

Parameters