10th Class Mathematics Triangles Question Bank MCQs - Triangles

  • question_answer
     
    In the adjoining figure, \[\frac{PS}{SQ}=\frac{PT}{TR}\] and \[\angle PST=\angle PRQ\]. Then, \[\Delta PQR\] is an

    A) equilateral triangle

    B) right angle triangle

    C) isosceles triangle

    D) Cannot say

    Correct Answer: C

    Solution :

    Given, \[\frac{PS}{SQ}=\frac{PT}{TR}\] and      \[\angle PST=\angle PRQ\]
     Since,   \[\frac{PS}{SQ}=\frac{PT}{TR}\]
     \[\therefore \,\,\,\,ST\,\,|\,\,|\,\,QR\]
                            [by converse of basic proportionality theorem]
    Then,     \[\angle PST\,\,=\angle PQR\]
                            [corresponding angles]                  ...(i)
    Also,        \[\angle PST\,\,=\angle PRQ\]               [given]   ...(ii)
    From Eqs. (i) and (ii), we get
                \[\angle PRQ=\angle PQR\]
    \[\Rightarrow \,\,\,\,PQ=PR\]
    [since, sides opposite to equal angles of a triangle are also equal]
    Hence, \[\Delta PQR\] is an isosceles triangle.
     


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