JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Trigonometrical ratios of multiple and sub multiple angles

  • question_answer
    \[(\sec 2A+1){{\sec }^{2}}A=\]

    A) \[\sec A\]

    B) \[2\sec A\]

    C) \[\sec 2A\]

    D) \[2\sec 2A\]

    Correct Answer: D

    Solution :

    \[(\sec 2A+1){{\sec }^{2}}A=\left( \frac{1+{{\tan }^{2}}A}{1-{{\tan }^{2}}A}+1 \right)\,(1+{{\tan }^{2}}A)\] \[=\frac{2\,(1+{{\tan }^{2}}A)}{1-{{\tan }^{2}}A}=2\sec 2A.\]


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