See instead ( for instance ) this diagram; if you complete the ( right ) triangle formed by the radius to a point on the surface, a line through that point parallel to the equatorial plane, and a portion of the axis, you will see that the distance from the surface point to the axis is R \ sin \ theta ( your " ? " is the colatitude that mathematicians typically use ).
22.
Where \ theta is colatitude and \ lambda is longitude, t is time, \ rho _ i and \ rho _ w are the densities of ice and water, respectively, \ gamma is the reference surface gravity, G _ s = G _ s ( h, k ) is the sea level Green s function ( dependent upon the h and k viscoelastic load deformation coefficients-LDCs ), I = I ( \ theta, \ lambda, t ) is the ice thickness variation, S ^ E = S ^ E ( t ) represents the eustatic term ( i . e . the ocean averaged value of S ), \ otimes _ i and \ otimes _ o denote spatio-temporal convolutions over the ice-and ocean-covered regions, and the overbar indicates an average over the surface of the oceans that ensures mass conservation.
