JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Fundamental trigonometrical ratios and functions, Trigonometrical ratio of allied angles

  • question_answer
    \[(m+2)\sin \theta +(2m-1)\cos \theta =2m+1,\]if

    A) \[\tan \theta =\frac{3}{4}\]

    B) \[\tan \theta =\frac{4}{3}\]

    C) \[\tan \theta =\frac{2m}{{{m}^{2}}+1}\]

    D) None of these

    Correct Answer: B

    Solution :

    Squaring the given relation and putting \[\tan \theta =t,\] \[{{(m+2)}^{2}}\,{{t}^{2}}+2(m+2)\,(2m-1)t+{{(2m-1)}^{2}}={{(2m+1)}^{2}}\,(1+{{t}^{2}})\] \[\Rightarrow \,3\,(1-{{m}^{2}})\,{{t}^{2}}+(4{{m}^{2}}+6m-4)\,t-8m=0\] \[\Rightarrow \,(3t-4)\,[(1-{{m}^{2}})\,t+2m]=0\], which is true if \[t=\tan \theta =\frac{4}{3}\] or \[\tan \theta =\frac{2m}{{{m}^{2}}-1}\].


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