c=2pir
circumfrence is distance around
so 1/4 of that is(2pir)/4=pir/2
and the 2 sides are radii
that quarter circle perimiter is 2r+c/4 or 2r+pir/2
10.71=2r+pir/2
times 2both sides
21.42=4r+pir
undistribute
21.42=r(4+pi)
divide both sides by 4+pi
(21.42)/(4+pi)=r
aprox pi=3.141592
r=2.99783 meters
aprox
r=3meters about
