Where on the earth's surface , the value of angle of dip is `90^(@)` ?

Where on the earth's surfaces is the value of angle of dip maximum?

Where on the earth's surface is the value of (i) angle of dip maximum (ii) vertical component of earth's magnetic field zero ?

Angle of dip is 90^@ at

Angle of dip is 90^@ at:

Where on the surface of the earth , the value of angle of dip is zero ?