Step 1: Find the area of the whole circle
A = pi x r^2
A = pi x 12^2
A = 144pi units^2
Step 2: Use the given angle to find only a part of the area
---The whole circle is 360 degrees, we only want 45 degrees.
45/360 x 144pi
1.5pi
4.71 units^2
Hope this helps!