CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The value of\[4\text{ }sin\text{ }A\text{ }co{{s}^{3}}A-4\text{ }cos\text{ }A\text{ }si{{n}^{3}}A\]is equal to:

    A)  \[cos\text{ }2A\]            

    B)  \[sin\text{ }3A\]

    C)  \[sin\text{ }2A\]         

    D)         \[cos\text{ }4A\]

    E)  \[sin\text{ }4A\]

    Correct Answer: E

    Solution :

    \[4\text{ }sin\text{ }A\text{ }co{{s}^{3}}A-4\text{ }cos\text{ }A\text{ }si{{n}^{3}}\text{ }A\] \[=4\text{ }sin\text{ }A\text{ }cos\text{ }A\text{ }(co{{s}^{2}}A-si{{n}^{2}}A)\] \[=2\text{ }sin\text{ }2A\text{ }cos\text{ }2A=sin\text{ }4A\]


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