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JEE Main & Advanced Sample Paper JEE Main Sample Paper-34

  • question_answer
    Let A and B denote the statements
    \[A:\,\,\cos {{\theta }_{1}}+\cos {{\theta }_{2}}+\cos {{\theta }_{3}}=0\]
    \[B:\,sin{{\theta }_{1}}+sin{{\theta }_{2}}+sin{{\theta }_{3}}=0\].
    If  \[\cos ({{\theta }_{1}}-{{\theta }_{2}})+\cos ({{\theta }_{2}}-{{\theta }_{3}})+\cos ({{\theta }_{3}}-{{\theta }_{1}})=\frac{-3}{2},\], then

    A)  A is true and B is false

    B)  A is false and B is true

    C)  both A and B are true

    D)  both A and B are false

    Correct Answer: C

    Solution :

    \[{{(\cos {{\theta }_{1}}+\cos {{\theta }_{2}}+\cos {{\theta }_{3}})}^{2}}+{{(\sin {{\theta }_{1}}+\sin {{\theta }_{2}}+\sin {{\theta }_{3}})}^{2}}=0\]


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