Algebra 2 (1st Edition)

$0.5$ units
Plugging in $S=\frac{3\pi}{4}$ into the formula from a) we get: $r=\frac{1}{\sqrt\pi}\sqrt{\frac{3\pi}{4}+\frac{\pi}{4}}-0.5=\frac{1}{\sqrt\pi}\sqrt{\pi}-0.5=1-0.5=0.5$