Magnitude/direction of point charges

[ajmCane22]

Homework Statement

(a) Find the magnitude and direction of the net electrostatic force exerted on the point charge q3 in the figure below. Let q = +1.5 µC and d = 27 cm.

http://www.webassign.net/walker/19-31.gif

Homework Equations

The Attempt at a Solution

I found Fx = 1.7 N and Fy = 3.3 N. So the total magnitude was 3.3 N. This part was correct, however when I tried to find the magnitude usting tan^-1(Fy/Fx) = tan^-1(3.3/1.7) = 62.74 degress the answer is wrong. It says I'm within 10%, but still wrong. I don't understand why. Please help

 

[SammyS]

Homework Statement

(a) Find the magnitude and direction of the net electrostatic force exerted on the point charge q3 in the figure below. Let q = +1.5 µC and d = 27 cm.

http://www.webassign.net/walker/19-31.gif

The Attempt at a Solution

I found Fx = 1.7 N and Fy = 3.3 N. So the total magnitude was 3.3 N. This part was correct, however when I tried to find the magnitude using tan^-1(Fy/Fx) = tan^-1(3.3/1.7) = 62.74 degrees the answer is wrong. It says I'm within 10%, but still wrong. I don't understand why. Please help

If F_x = 1.7 N and F_y = 3.3 N , then the magnitude of F cannot be 3.3 N

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