SSC Sample Paper SSC CHSL (10+2) Sample Test Paper-7

  • question_answer
    If \[\alpha +\beta \] = \[90{}^\circ \], then cosec2 a +cosec2\[\beta \] =

    A) sec2a

    B) cosec2a+ sec2\[\beta \]

    C) cosec2  \[\alpha \] cosec2 \[\beta \]

    D)  sec2 \[\alpha \]  cosec2 \[\beta \]

    Correct Answer: C

    Solution :

     \[cose{{c}^{2\text{ }}}\alpha +cose{{c}^{2}}\text{ }\beta \] \[=\frac{1}{{{\sin }^{2}}\alpha }+\frac{1}{{{\sin }^{2}}\beta }\] \[=\frac{{{\sin }^{2}}\beta +{{\sin }^{2}}a}{{{\sin }^{2}}\alpha .{{\sin }^{2}}\beta }\] \[=\frac{{{\cos }^{2}}\alpha +{{\sin }^{2}}a}{{{\sin }^{2}}\alpha .{{\sin }^{2}}\beta }\] \[[\because \alpha +\beta =90{}^\circ \Rightarrow \sin \,\beta =\sin (90{}^\circ -\alpha )=\cos \alpha ]\] \[=\frac{1}{{{\sin }^{2}}\alpha .{{\sin }^{2}}\beta }\] \[={{\operatorname{cosec}}^{2}}\alpha .\cos e{{c}^{2}}\beta .\]


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