Calculating Electric Field at Point A from Uniformly Charged Arc

[martinbandung]

Homework Statement

Find electric field at Point A
its an arc with uniform density= lamda

https://drive.google.com/file/d/14cBqE2dMe_w0nb9LtPG0h1cUOrzGWt6g/view?usp=sharing
the problem

Homework Equations

E=intergal dq/r^2

The Attempt at a Solution

I've tried using wolfram and cosine rule to determine the distance from the arc to point A
but it give imaginary result

 

[scottdave]

It appears that your Google drive image doesn't have the proper permissions for me to view it, so I cannot comment yet. Can you post the formula which you typed into Wolfram?

 

[rude man]

Point A isn't well defined on your pic but it's apparently along the y axis. Neither is it clear whether the arc is a semicircler or other symmetrical arc. You obviouslly need to know the equation of the arc and where A really is located.

In any case, take advantage of symmetry to eliminate the x component of mirror points along the arc to get the Ey-axis E field. It's high school geometry.