9th Class Mathematics Circles Question Bank Circle

  • question_answer
    In the given figure below, if \[\angle BAD={{50}^{{}^\circ }},\text{ }\angle ADC={{115}^{{}^\circ }}\] then \[\angle DPC\] is

    A)  \[{{40}^{{}^\circ }}\]                       

    B)  \[{{65}^{{}^\circ }}\]    

    C)  \[{{50}^{{}^\circ }}\]                                   

    D)  \[{{60}^{{}^\circ }}\]

    Correct Answer: B

    Solution :

    (b):- Given, \[\angle BAD={{50}^{{}^\circ }},\text{ }\angle ADC={{115}^{{}^\circ }}\] in cyclic quadrilateral ABCD. \[\angle BAD+\angle BCD={{180}^{{}^\circ }}\] \[\Rightarrow \]  \[\angle BCD={{180}^{{}^\circ }}-{{50}^{{}^\circ }}={{130}^{{}^\circ }}\] Now \[\angle BCD+\angle DCP={{180}^{{}^\circ }}\]       (Straight line) \[\angle DCP={{180}^{{}^\circ }}-{{130}^{{}^\circ }}={{50}^{{}^\circ }}\] And     \[\angle ADC+\angle CDP={{180}^{{}^\circ }}\]     (Straight line) \[{{115}^{{}^\circ }}+\angle CDP={{180}^{{}^\circ }}\Rightarrow \angle CDP={{65}^{{}^\circ }}\] Now in \[\Delta CPD\]. \[\angle DCP+\angle CDP+\angle DPC={{180}^{{}^\circ }}\] \[\Rightarrow \]\[{{50}^{{}^\circ }}+{{65}^{{}^\circ }}+\angle DPC={{180}^{{}^\circ }}\] \[\angle DPC={{180}^{{}^\circ }}-{{115}^{{}^\circ }}={{65}^{{}^\circ }}\]        


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