In spherical polar coordinates (γ, θ, α), θ denotes the polar angle around z–axis and α denotes the azimuthal angle raised from x–axis. The Cartesian coordinates can be retrieved from spherical coordinates (γ, θ, α) by: X = r.sinθ.cosα Y = r.sinθ.sinα Z = r.sinθ Then the y–component of P is given by P.sinθ.sinα