Problem 10-31(a) Vector electric field

Diagram indicating the  positions of two particles.

The figure shows the positions of two a particles (charge on each is \(+2e\)) and an electron. What are the magnitude and direction of
(a) the resultant force on the electron?
(Hint: choose the \(+x\) axis along the line from the electron to the right-hand a particle.)

[Ans.(a) \(1.31 \times 10^{-8} N\) at \(13.3^\circ\) to left of line from electron to right-hand a]

We are going to evaluate the force using components so we need to choose an \(x, y\) coordinate system. There is no such thing as a "wrong" coordinate system but some are better than others because they simplify the solution. Which is best?

Four possible coordinate systems A, B, C, D.