` l and m` are two parallel tangents to a circle with centre O, touching the circle at A and B respectively. Another tangent at C intersects the line `l` at D and m at E. Prove that` /_DOE=90^@.`

X Y and Xprime Yprime are two parallel tangents to a circle with centre O and another tangent AB with point of contact C intersecting X Y at A and XprimeYprime at B. Prove that /_A O B\ =\ 90^0

In the given figure 4.13 ,xy and x'y' are two parallel tangents to a circle with centre O and another tangent AB with point of contact C intersecting xy at A and x'y' at B. Prove that angle AOB =90^@ .

In Fig, 10.13, XY and X'Y' are two parallel tangents to a circle with centre O and another tangent AR with point of contact C intersecting XY at A and X'Y' at B. Prove that angle AOB=90^@ .

If two parallel tangents drawn to a circle with centre O are intersected at the points D and E respectively by a tangent drawn at another point on the circle,then show that angleDOE=90^@

In Fig.10.13 , and and are two parallel tangents to a circle with centre O and another tangent AB with point of contact C intersecting contact C intersecting at B.Prove that /_AOB=90^(@)

PQ and RS are two parallel tangents to a circle with centre O and another tangent AB wih point of contact C intersect PQ at A and RS at B. then find angle AOB

PM is a tangent to a circle with centre O touching the circle at M. If OP=85cm and PM=77cm, find the radius of the circle.

In Fig.10.13, XYandX'Y' are two parallel tangent to a circle with centre O and another tangent AB with point of contact C intersecting XY at A and X'Y' at B.Prove that angleAOB=90^@ .