How is net direction of magnetic field is obtained like in illustration 15 iiird case 2 are out of page and one into the page then how it is decided that final B will be into the page
The one which has highest magnitude will dominate direction here as (angle b/w all vectors here is 0,π)
I also getting similar expression as you but without π
Yes thank you for telling there will be no pi in final i just noticed one mistake.
Question 12 i am stuck at this integration what to substitute to find integration to get magnetic field.
Substitute r=x tan theta