
#1
Feb2612, 05:59 PM

P: 123

I'm doing example 2.1 in Griffith's Electrodynamics book. Can someone explain where the cos(theta) comes from in the formula for dE? The formula is on the first image: Here.




#2
Feb2612, 06:20 PM

P: 123

SOLVED:
I see what's going on. If you add the r_hat vectors you end up with 2(z/r)z_hat. z/r=cos(theta). So we end up with 2cos(theta)z_hat. 



#3
Feb2612, 06:32 PM

P: 28

that looks so hard. are you supposed to figure out that formula all by yourself



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