# Difficult magnetism question

#### Physicsstudent10121

If anybody could provide insight on this question it would be greatly appreciated, thank you.

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#### studiot

I only have time to get you started tonight.

The idea is to consider a small element ds of the total length of wire S.
This is connected angle φ at P between the perpendicular to P and ds as shown, with the zero at the perpendicular.
This is geometry.
Use the formula given to calculate the flux at P due to ds and integrate from φ = 0 to φ= (90 - θ2).
This gives the part of the flux generated on the right hand side of the perpendicular.
Do the same on the left hand side using φ = 0 to (θ1-90) as the limit.
So you change the variable from dB to ds and finally dφ using the formula given and the geometry.