In spherical polar coordinates (l, q, a), q denotes the polar angle around z-axis and a denotes the azimuthal angle raised from x-axis . Then the y-component of P is given by

In the spherical polar coordinate system described, the position of a point P is defined by its distance from the origin (l), the polar angle (q) measured from the z-axis, and the azimuthal angle (a) measured from the x-axis. According to standard coordinate conversion formulas, the projection of the radial distance onto the xy-plane is given by l sin(q). To find the y-component, this projection is further resolved along the y-axis using the sine of the azimuthal angle (a). Therefore, the Cartesian y-component is expressed as y = l sin(q) sin(a). While the question uses (l, q, a) instead of the conventional (r, θ, φ), the geometric relationships remain identical: x = l sin(q) cos(a), y = l sin(q) sin(a), and z = l cos(q). Thus, the y-component of P is P sinq sina.