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. Then the y-component of P⃗ is given by

- Spherical coordinates typically use (r, θ, φ) or (ρ, θ, φ). The question uses (γ, θ, α) with meanings specified. - γ (or P) is the magnitude. - θ is the angle from the z-axis (polar angle). - α is the angle from the x-axis in the xy-plane (azimuthal angle). - The projection onto the xy-plane has length $P\sin\theta$. - This projection is resolved into x and y components using the azimuthal angle α.