 #1
MatinSAR
 129
 37
 Homework Statement:
 How can I find "dx" in a straight line of electric charge?(Details in Picture)
 Relevant Equations:

r=R/cos(teta)
x=rtan(teta)
This is the question ... I have it's solution ...
My problem : I can't understand why dx=R/cos^2(teta) dteta
I have thought many hours but I couldn't find it's reason ... Can anyone please help with this ?!