Hello from MrBillDoesMath!
Answer: 48.2 degrees
Discussion:
In the diagram, "6" is the x- distance along the side adjacent to theta, and
3 * sqrt(5) is the y-distance along the side opposite angle theta.
By definition of tangent of angle, using "@" for theta, we have
tan (@) = opposite/adjacent = 3 * sqrt(5) / 6 = sqrt(5)/2
So @ = (inverse tangent (sqrt(5)/2) ) = 48.189 degrees (approximately)
Thank you,
MrB