PQ is tangent to outer circle and PR is tangent to inner circle. if PQ=4cm,OQ=3cm and OR=2cm then the length of PR is
visit here to view the FIGURE "sumspics.blogspot.in"
in above website check "p1"
given PQ = 4, OQ = 3, OR= 2
from above figure
triangle OQP is a right angled triangle
note: Tangents touches the circle at right angles
by pythagoras OP2=OQ2+PQ2
OP = 5
similarly OPR is a right angled triangle
25 = 4 + PR2
PR = root (21)