Is the Electric Field Calculation for an Infinite Sheet Correct?

[Planck const]

Homework Statement

What is the field?
I just want you to chek my solution (just the begining) (math)

You can see the paint.

Homework Equations

Coulomb rule

The Attempt at a Solution

1.
tan(Tetha) = r/a
=> r = a*tan(Tetha)
=> dr = a/cos^2(Tetha)d(Tetha)
2.
dq = Sigma * da = 2Pi*Sigma*rdr =
= 2Pi*Sigma*r*a/cos^2(Tetha)d(Tetha)
3.
cos(Tetha) = a/R
=>1/R^2 = cos^2(Tetha)/a^2
4.
dEy (the enqual) = dE * cos(Tetha)
5.
The limits of the integral are... from Tetha = 0 to Tetha = 90 deg (?)

I ask you... am I right?

Thanks for the watchers :)

 

[Nate810]

Yes, you are correct so far. The next step would be to calculate the integral, using the equations and limits you have provided. The result of the integral will be the field.