CBSE Class 10 Mathematics Basic sample paper 2023-24: question 29
From the official CBSE sample question paper for 2023-24, section C, question 29, for 3 marks. Try it first; the hints and our step-by-step solution are below.
Q29 · 3 marks · Short answerCircles
A circle touches all the four sides of quadrilateral ABCD. Prove that .
Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.
Hints
Open one hint at a time and try again before the next.
Hint 1
Each vertex of the quadrilateral is an external point from which two tangents are drawn to the circle.
Hint 2
Write the four pairs of equal tangent lengths, add them, and regroup the segments into the sides.
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
- 1 mark
Given: A circle touches sides AB, BC, CD and DA of quadrilateral ABCD at P, Q, R and S respectively. To prove: . (Figure: quadrilateral ABCD with the inscribed circle touching AB at P, BC at Q, CD at R and DA at S.)
- 1 mark
Tangents drawn from an external point to a circle are equal in length, so:
...(1), ...(2), ...(3), ...(4) - 1 mark
Adding (1) to (4):
. Hence proved.
Answer: proved using equal tangents from external points
Where the marks are
- Given, to prove and labelled figure (1 mark)
- Four pairs of equal tangents with reason (1 mark)
- Adds the equalities and regroups to get the result (1 mark)
Revise the chapter
- Chapter: Circles (notes, formulas, where marks are lost and every past question)
- Topic: Solving Problems Using Tangent Properties
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