Apparent dip is -1- When the dip circle by 900- the apparent dip becomes -2- Declination - at the place prior to 900 rotation is given by

The needle of a dip circle shows an apparent dip of $45^{0}$ in a particular position and $53^{0}$ when the circle is rotated through $90^{0}$ . Find the true dip.

The plane of the dip circle is set in the geometric meridian and the apparent dip is $θ_{1}$ . It is then set in a vertical plane perpendicular to geographic meridian. The apparent dip is $θ_{2}$ . The declination $δ$ at the place is :

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Apparent dip is δ1. When the dip circle by 900, the apparent dip becomes δ2. Declination α at the place (prior to 900 rotation) is given by

The correct option is B cosα=tanδ1/tanδ2tanθ‘=tanθcosαtanδ2=tanδ1cosαcosα=tanδ1tanδ2Hence option 'B' is correct.

Apparent dip is $δ_{1}$ . When the dip circle by $90^{0}$ , the apparent dip becomes $δ_{2}$ . Declination $α$ at the place (prior to $90^{0}$ rotation) is given by

The correct option is B $c o s α = t a n δ_{1} / t a n δ_{2}$
$tan θ^{‘} = \frac{tan θ}{cos α}$
$tan δ_{2} = \frac{tan δ_{1}}{cos α}$
$cos α = \frac{tan δ_{1}}{tan δ_{2}}$
Hence option 'B' is correct.