7th Class Mathematics Lines and Angles Question Bank Lines & Angles

  • question_answer
    Complementary angle of an angle greater than \[45{}^\circ \] is.

    A)  Less than \[45{}^\circ \]

    B)  Equal to \[45{}^\circ \]    

    C)  Greater than \[45{}^\circ \]    

    D)  Equal to \[90{}^\circ \]

    Correct Answer: A

    Solution :

    (a): Let angle \[\angle a>45{}^\circ \]: Its complementary angle, say \[\angle b=90-\angle a\,\,\,\,\angle a>45{}^\circ \] \[\therefore \,\,\,\,\,-\angle a<-45{}^\circ \] Add \[90{}^\circ \]to both sides \[\Rightarrow \] \[=\,\,90{}^\circ -\angle a\,\,\,<90{}^\circ -45{}^\circ \] \[\Rightarrow \,\,\angle b\,=90{}^\circ -\angle a<45{}^\circ \] Note: This technique of dealing with inequalities \[\,\angle a>45{}^\circ \Rightarrow \,\,-\,\angle a<-45{}^\circ \] should be learnt and remembered for future applications.


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