7th Class Mathematics The Triangle and its Properties Question Bank The Triangle and Its Properties

  • question_answer
    In the figure (not drawn to scale), ABC is an equilateral triangle and ABD is an isosceles triangle with DA = DB, find x.

    A)  \[{{14}^{o}}\]                    

    B)  \[{{16}^{o}}\]                    

    C)  \[{{12}^{o}}\]             

    D)  \[{{32}^{o}}\]                                

    Correct Answer: A

    Solution :

    Since ABC is an equilateral triangle. \[\therefore \] \[\angle CAB=\angle ABC=\angle BCA={{60}^{o}}\] And \[\angle DBA=\angle DAB=({{60}^{o}}-x)\] \[[\because \,\,DA=DB]\] In \[\Delta \,DAB,\] \[\angle DAB\angle DAB+\angle ADB={{180}^{o}}\]             \[\Rightarrow \] \[2({{60}^{o}}-x)+{{88}^{o}}={{180}^{o}}\] \[\Rightarrow \] \[2({{60}^{o}}-x)={{92}^{o}}\Rightarrow {{60}^{o}}-x={{46}^{o}}\Rightarrow x={{14}^{o}}\]


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