The real angle of dip, if a magnet is suspended at an angle of `30^(@)` to the magnetic meridian and the dip needle makes an angle of `45^(@)` with horizontal, is:

Explanation

Here, `theta=30^@`, Apparent value of dip, `delta_1=45^@`, Actual value of dip, `delta=?`
If H is horizontal component of earth's magnetic field in magnetic meridian, then
`tandelta=(V)/(H)`
Let `H_1` be component of H at `30^@` to magnetic meridian, then
`tandelta_1=(V)/(H_1)=(V)/(Hcostheta)=(tandelta)/(cos theta)`
or `tandelta=tandelta_1xxcostheta=tan45^@xxcos30^@`
`=1xxsqrt3/2=(1*732)/(2)=0*866`
`:. delta=tan^-1(0*866)=40*9^@`