10th Class Mathematics Introduction to Trigonometry Question Bank MCQs - Introduction to Trigonometry

  • question_answer
    If \[\sin \theta -\cos \theta =0\], then the value of \[{{\sin }^{4}}\theta +{{\cos }^{4}}\theta \] will be

    A) \[\frac{1}{4}\]

    B) \[\frac{1}{2}\]

    C) \[\frac{3}{4}\]

    D) 1

    Correct Answer: B

    Solution :

    Given, \[\sin \,\theta -\cos \theta =0\] \[\Rightarrow \,\,\sin \theta =\cos \theta \] \[\Rightarrow \,\tan \theta =1=\tan \,45{}^\circ \Rightarrow \theta =45{}^\circ \] \[\therefore \,\,\,{{\sin }^{4}}\theta +{{\cos }^{4}}\theta ={{\sin }^{4}}45{}^\circ +{{\cos }^{4}}45{}^\circ \] \[={{\left( \frac{1}{\sqrt{2}} \right)}^{4}}+{{\left( \frac{1}{\sqrt{2}} \right)}^{4}}=\frac{1}{4}+\frac{1}{4}=\frac{1}{2}\]


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