\(r = {\sqrt{8^2-15^2}}\)
r=sqrt(8^2 - 15^2) Square both sides
r^2 =(8^2 - 15^2)
r^2 =(64 - 225)
r^2=-161 =-1 x 161 Take the sqrt of both sides
r =i sqrt(161)
r =12.688577 i
