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## Homework Statement

What are the magnitude and direction (in degrees counterclockwise from the horizontal) of the electric field at the center of the square of Fig. 23-31 if q = 0.9*10^-8 C and a = 5.1 cm?

http://personalpages.tds.net/~locowise/23-30.gif

## Homework Equations

E=kq/r^2

k=8.99*10^9 N*m^2/C^2

## The Attempt at a Solution

Calculated r using the pythagorean theorem:

5.1cm--->.051m

sqrt(.051^2+.051^2)=.07212m ...this is the length of the entire diagonal so r would be the diagonal divided by 2 which equals .036062445841 meters.

Starting with E1 (the upper left hand corner of the square) and moving clockwise to E4...

E1=+62214.53 N/C

E2=-124429.07 N/C

E3=+124429.07 N/C

E4=-62214.53 N/C

Here is where I get confused...do I resolve these in horizontal and vertical components? And, how do I find the angle? Thanks for your help!

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