Physics help ~~?

https://session.masteringphysics.com/problemAsset/1000283558/2/21-93.jpg

A uniformly charged disk has radius 2.50 cm and carries a total charge of 3.0×10^−12 C

Part A
Find the magnitude of the electric field on the x-axis at x = 20.0 cm

E = 0.67 N/C (Ans.)


Part B
Find the direction of the electric field on the x-axis at x = 20.0 cm.

θ = _________ ∘ counterclockwise from the +x-direction


I did Part A correctly, need help with Part B. Thanks a lot for helping.