At a place, the horizontal component of earth's magnetic field is $4 × 10^{-4}T$ and angle of dip is 60°. The value of horizontal component of earth's magnetic field at the equator is:

$\sqrt{2} × 10^{-4} T$ $2×10^{-4} T$ Zero $8×10^{-4} T$

$8×10^{-4} T$

The correct answer is Option (4) → $8×10^{-4} T$