# Maths trigonometry

posted by
**forest** on
.

using basic trigonometry derive the following equations, which are used to convert cartesian to polar coordinates and vice versa. why is the cos(phi)in the x term?

x = R cos (phi) sin (lamda)

y = R sin (phi)

they are used in orthogonal projection of a spherical surface to a flat surface in the (x y) plane.

where (phi)=latitude

(lamda)=longitude