10th Class Mathematics Introduction to Trigonometry Question Bank Trigonometry

  • question_answer
    The expression \[3{{(\sin x-\cos x)}^{4}}+6{{(sinx+\cos x)}^{2}}+4(si{{n}^{6}}x+{{\cos }^{6}}x)\] is equal to

    A) 10

    B) 11

    C) 12

    D) 13

    Correct Answer: D

    Solution :

     Given expression \[=3{{[{{(\sin x-\cos x)}^{2}}]}^{2}}+\] \[6{{(\sin c+\cos x)}^{2}}+4({{\sin }^{6}}x+{{\cos }^{6}}x)\] \[=3{{[{{\sin }^{2}}x+{{\cos }^{2}}x-2\sin x\,\cos x]}^{2}}+6[{{\sin }^{2}}x+{{\cos }^{2}}x\]\[+2\sin x\,\cos x]\] \[+4[({{\sin }^{2}}x+{{\cos }^{2}}x)\,({{\sin }^{2}}x+{{\cos }^{2}}x-{{\sin }^{2}}x\,{{\cos }^{2}}x]\] \[=3{{[1-\sin 2x]}^{2}}+6[1+\sin 2x]\] \[+4\times 1\times [{{({{\sin }^{2}}x+{{\cos }^{2}}x)}^{2}}-3{{\sin }^{2}}x{{\cos }^{2}}x]\] \[=3[1+{{\sin }^{2}}2x-2\sin 2x]+6+6\sin 2x\]                                                 \[+(4-3\,{{\sin }^{2}}2x\] \[=13\]


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