If θ1 and θ2 be the apparent angles of dip observed in

If θ₁ and θ₂ be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip θ is given by :-

1. tan¹θ = tan¹θ₁ + tan¹θ₂
2. cot¹θ = cot¹θ₁ – cot¹θ₂
3. tan¹θ = tan¹θ₁ – tan¹θ₂
4. cot¹θ = cot¹θ₁ + cot¹θ₂

If θ₁ and θ₂ are opparent angles of dip
Let α be the angle which one of the plane make with the magnetic meridian.

tan θ₁ =	υ
	H cos α

i.e.,cos α =	υ	....(i)
	H tan θ₁

tan θ₂ =	υ	,
	H sin α

i.e.,sin α =	υ	....(ii)
	H tan θ₂

Squaring and adding (i) and (ii), we get

i.e., 1 =	V²	[cot²θ₁ - cot²θ₂]
	H²

i.e., cot² θ = cot²θ₁ + cot² θ₂