2. Questions Bank
  3. JEE Main & Advanced
  4. Mathematics
  5. Trigonometric Identities

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

  • question_answer
    If \[\sin x+{{\sin }^{2}}x=1,\]then \[{{\cos }^{8}}x+2{{\cos }^{6}}x+{{\cos }^{4}}x=\]

    A) 0

    B) -1

    C) 2

    D) 1

    Correct Answer: D

    Solution :

    We have \[\sin x+{{\sin }^{2}}x=1\,\,\Rightarrow \,\,\sin x={{\cos }^{2}}x\] \ \[{{\cos }^{8}}x+2{{\cos }^{6}}x+{{\cos }^{4}}x={{\sin }^{4}}x+2{{\sin }^{3}}x+{{\sin }^{2}}x\] \[={{(\sin x+{{\sin }^{2}}x)}^{2}}=1\].


You need to login to perform this action.
You will be redirected in 3 sec spinner