8th Class Mathematics Practical Geometry Question Bank Geometry

  • question_answer
    In the figure BD = DC and\[{{50}^{o}}\]. The value of \[{{85}^{o}}\]is:

    A)  \[{{120}^{o}}\]                  

    B)  \[{{360}^{o}}\]

    C)  \[{{90}^{o}}\]                    

    D)  \[{{90}^{o}}\]

    Correct Answer: C

    Solution :

    Since, \[{{45}^{o}}\] in \[{{60}^{o}}\] Therefore, \[{{75}^{o}}\] is an isosceles \[\angle CAD={{50}^{o}}\]. Now, by the property of isosceles \[\angle BED={{120}^{o}}\]. \[\angle BCD\] Now, \[{{75}^{o}}\] (Sum of angles of\[{{105}^{o}}\]) Now, ABCD is a cyclic quadrilateral \[{{85}^{o}}\] \[{{60}^{o}}\] \[\angle BAC={{45}^{o}}\] \[\Rightarrow \]\[\angle A=\angle BAC=50{}^\circ .\]


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