1. The problem statement, all variables and given/known data This is problem 47(chapter 21) in the text book - Physics for engineers and scientists (Giancoli) Uniformly charged wire has length L, where point 0 is the mid point. Show that the field at P, perpendicular distance x from 0 is E= (lambda/2*pi*epsilon_0) *(L/x*sqrt(L^2+4x^2) 2. Relevant equations 3. The attempt at a solution I tried solving it, I got E = - (lambda/2pi*epsilon_0)*[1/sqrt(L^2+4x^2)-1/2x) Is something wrong with my integration? My attempt is correct until E= lamda/r^2*4pi*epsilon_0 * integration (cos theta)dl After this, I use cos theta = x/r (r is the hypotenuse = sqrt (L^2+4x^2)) I am trying to do this instead of taking r=x cos theta.