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Summer Clouds

16/06/2017 at 17:03
Answers
3
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In the figure on the right, QSR is a straight line, \(\angle QPS=12^o\) and \(PQ=PS=RS\). What is the size of angle QPR?
        P Q S R 12 o
A. \(36^o\)
B. \(42^o\)
C. \(54^o\)
D. \(60^o\)




    List of answers
  • ...
    Phan Minh Anh 20/06/2017 at 09:37

    The answer is C

  • ...
    Phan Thanh Tinh Coordinator 16/06/2017 at 17:26

    \(\Delta PQS\) has PQ = PS,so \(\Delta PQS\) isosceles at P

    \(\Rightarrow\widehat{Q}=\widehat{PSQ}\) but \(\widehat{QPS}+\widehat{Q}+\widehat{PSQ}=180^0\)

    \(\Rightarrow2\widehat{PSQ}+12^0=180^0\Rightarrow\widehat{PSQ}=84^0\)

    \(\Delta PSR\) has SP = SR,so \(\Delta PSR\) isosceles at S

    \(\Rightarrow\widehat{SPR}=\widehat{R}\)

    \(\widehat{PSQ}\) is the exterior angle of \(\Delta PSR\Rightarrow\widehat{PSQ}=\widehat{SPR}+\widehat{R}\)

    \(\Rightarrow2\widehat{SPR}=84^0\Rightarrow\widehat{SPR}=42^0\Rightarrow\widehat{QPR}=12^0+42^0=54^0\)

    Hence,the answer is C

  • ...
    Thu Thảo 17/06/2017 at 21:38

    \(\Delta PQS\) has: \(PQ=PS\)

    \(\Rightarrow\)​\(\Delta PQS\) is an ​ isosceles triangle.

    \(\Rightarrow\)\(\widehat{PSQ}=\frac{180^0-\widehat{QPS}}{2}\)

    \(\Rightarrow\)\(\widehat{PSQ}=84^0\)

    \(\Rightarrow\)\(\widehat{PSR}=180^0-84^0=96^0\)

    \(\Delta PSR\) has: \(SP=SR\)

    \(\Rightarrow\)\(\Delta PSR\) is an isosceles triangle

    \(\Rightarrow\)\(\widehat{SPR}=\frac{180^0-\widehat{PSR}}{2}\)

    \(\Rightarrow\)\(\widehat{SPR}=42^0\)

    \(\Rightarrow\)\(\widehat{QPR}=12^0+42^0=54^0\)

    Answer: C.


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