The magnetic dip angle is defined as the angle between the direction of the earth's magnetic field and the tangent plane at the earth's surface. Derive an expression for the dip angle as a function of geomagnetic latitude, on the assumption that the induction is a dipole field.
The dip angle is the angle by how much the magnetic field dips toward the earth - we expect it to be zero near the equator and 
near the pole.
I will first assume that the geographic pole is aligned with the magnetic pole. And then I will write the magnetic dipole field in spherical coordinates and consider the surface of a sphere.
We have not yet discussed magnetic dipoles.