Consider a quarter of a circle of radius 81. Let r be the radius of the circle inscribed in this quarter of a circle. Find r.  Select the correct option
A) 86*(sqr2 -1)	B) 88*(sqr3 -1)	C) 4*(sqr7 - 1)	D) 81* (sqr2 -1)	E) None of these
I got 81/(sqr2 +1) and just forgot to multiply by (sqr2 -1).   Answer is 81* (sqr2 -1)
<result>D</result>
Consider a quarter of a circle of radius 81. Let r be the radius of the circle inscribed in this quarter of a circle. Find r.