d-=sin fol0cosfopsin foesinfopcos fo vecd = begin bmatrixsin theta cosphi sin theta sin phi cos theta endbmatrix

The given expression is a vector equation. It represents a vector d in terms of the variables theta and phi.

The vector d is defined as follows:

d = [sin(theta) cos(phi), sin(theta) sin(phi), cos(theta)]

This means that the components of the vector d are determined by the trigonometric functions of the variables theta and phi. The first component is sin(theta) cos(phi), the second component is sin(theta) sin(phi), and the third component is cos(theta).