Remember that
A complete circle has 360 degrees
A semicircle has 180 degrees
so
Applying proportion
100/180=x/225
solve for x
x=(100/180)*225
x=22,500/180
x=125%
Convert to fraction
125/100
simplify
5/4
therefore
the labeled angle represents 5/4
Part b
Express the labeled angle in radian measure
Remember that
pi radian -------> represents 180 degrees
so
225 degrees
radians=225pi/180
5pi/4