The angle of dip at a place on the earth gives.

Angle of dip is the angle made by the magnetic field of earth with the horizontal, i.e. the earth surface. It gives the direction of the earth's magnetic field.
Magnetic field being a vector, can be resolved into horizontal and vertical components. The horizontal component is parallel to the ground, so there is no question of any angle associated with it.
At any point on the earth surface, some geographical meridian always passes through it. It has no relation with the magnetic field. Whereas, the angle of dip is a parameter of the field.
The vertical component of the earth's magnetic field is always perpendicular to the ground, so the angle is always 90⁰.