Vectors and 2D Motion Physics Example Problem

Question

A flea pulls on a puck with force 7 microN at an angle of 45 degrees. Another flea pulls on the puck with force of 3 microN at an angle of -45 degrees. What's the magnitude of the net force on the puck?

I calculated the magnitude of the net force to be 7.6 uN, which is correct.

I'm not sure how to go about answering these two questions.

At what angle is the net force?

In what direction must the third flea pull so that the puck stops accelerating?

(I think for this one it would be -180 deg + (angle of net force) but I need to find net force)

Answer 1

Direction of resulting force: tanθ = (7sin45° - 3sin45°)/(7cos45° + 3cos45°) = 0.4;

θ = tan^-10.4 = 21.8° above positive x-axis. So, 3rd force has angle 201.8° with positive direction of positive x-axis