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PS is the bisector of ∠ QPR of ∆ PQR. Prove that QS/SR = PQ/PR.

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How to use the angle bisector theorem. How bisector is equal to the ratio of the other two sides.
Class 10th Maths EXERCISE 6.6,Page No:152, Questions No:1
NCERT Books for Session 2022-2023 are based on CBSE Board.

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1 Answer

  1. A line RT is drawn parallel to SP, which intersects QP produced at T.
    Given that, SP bisects angle QPR, therefore
    ∠QPS = ∠SPR …(1)
    By construction,
    ∠SPR = ∠PRT(As PS II TR) …(2)
    ∠QPS = ∠QTR(As PS II TR) …(3)
    From the above equations, we have
    ∠PRT = ∠QTR
    ∴ PT = PR
    By construction, PS II TR
    In ΔQTR, by Thales theorem
    QS/SR = QP/PT ⇒ QS/SR = PQ/PR [∵ PT = TR]

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