Prove that opposite sides of a quadrilateral circumscribing a cir

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 Multiple Choice QuestionsShort Answer Type

341.

In Figure 1, common tangents AB and CD to the two circles with centres O1 and O2 intersect at E. Prove that AB = CD.

               


342.

The incircle of an isosceles triangle ABC, in which AB = AC, touches the sides BC, CA and AB at D, E and F respectively. Prove that BD = DC.


 Multiple Choice QuestionsLong Answer Type

343.

Prove that the tangent at any point of a circle is perpendicular to the radius through the point of contact.


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344.

Prove that opposite sides of a quadrilateral circumscribing a circle subtend supplementary angles at the centre of the circle.


                      

Let ABCD be a quadrilateral circumscribing a circle centered at O such that it touches the circle at point  P, Q, R, S.

Let us join the vertices of the quadrilateral ABCD to the center of the circle.

Consider OAP and OAS, 

AP = AS  (Tangents from the same point)

OP = OS  (Radii of the same circle)

OA = OA  ( common side )

OAP  OAS     ( SSS congruence criterion )Therefore, AA, PS, OOAnd thus, POA = AOS1 = 8Similarly,2 = 34 = 56 = 71 + 2 + 3 + 4 + 5 + 6 + 7 + 8 =360°1 + 8   + 2 + 3  + 4 + 5  + 6 + 7  = 360°21 + 22 + 25 + 26 = 360°21 + 2  + 25 + 6 = 360°1 + 2 + 5 + 6 = 180°AOB + COD = 180°Similarly, we can prove that  BOC + DOA = 180° 

Hence, opposite sides of a quadrilateral circumscribing a circle subtend supplementary angles at the centre of the circle.


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 Multiple Choice QuestionsShort Answer Type

345.

If the angle between two tangents drawn from an external point P to a circle of radius a and centre O, is 60°, then find the length of OP.


346.

A circle touches all the four sides of a quadrilateral ABCD. Prove that 

AB + CD = BC + DA


347.

Prove that the tangents drawn at the end points of a chord of a circle make equal angles with the chord.


 Multiple Choice QuestionsLong Answer Type

348.

In the given figure, XY and X’Y’ are two parallel tangents to a circle with centre O and another tangents AB with point of contact C, is intersecting XY at A and X’Y’ at B. Prove that ∠AOB = 90°.

                  


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349.

Prove that the lengths of two tangents drawn from an external point to a circle are equal.


 Multiple Choice QuestionsMultiple Choice Questions

350.

In Fig., the sides AB, BC and CA of a triangle ABC, touch a circle at P, Q and R respectively. If PA = 4 cm, BP = 3 cm and AC = 11 cm, then the length of BC (in cm) is

                        

  • 11

  • 10

  • 14

  • 15


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