# Find the electric field distance z above one end o…

### Question Description:

Find the electric field distance z above one end of the straight line segment of length L which carry’s uniform charge Just have a few question about how to solve this, now i use coulomb law , de=(1/4pie*Eo)(Q/r^2) r^ using that formula theu got de=1/4pie*Eo (dQ/r^2) cos@ then plugs in, de=1/4pie Eo (y dx/(z^2+x^2))(z/(z^2+x^2)^1/2 y is the uniform charge. My question is why did they do this as in how did they figure out r^2= (z^2+x^2) that dq= ydx and that r^ = cos@ (note this is the x component then they do it for y and instead of cos they use sin)