Orthogonality can be verified by showing that the vector dot product is zero. The unit magnitude of these vectors is a consequence of Eq. 1. Using the tangent vector, the angle θ of the tangent to the curve is given by: sin ⁡ ⁡ θ θ = y ′ ( s ) x ′ ( s ) 2 + y ′ ( s ) 2 = y ′ ( s ) ; and cos ⁡ ⁡ θ θ = x ′ ( s ) x ′ ( s ) 2 + y ′ ( s ) 2 = x ′ ( s ) .