Find the angle in degrees first:
Substitute 180 for pi.
(5 x 180) / 4
900 / 4
= 225 degrees
Now, the angle that has the same sin value of 225 is the angle's reference angle, or the angle that it makes with the x-axis.
225-180 = 45
45 is the angle that shares the same sin value
Answer: 45 degrees
Hope this helps :)