CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2002

  • question_answer
    If\[\overrightarrow{a},\text{ }\overrightarrow{b},\text{ }\overrightarrow{c}\]are any three vectors, then \[[\overrightarrow{a}\,\text{+}\,\overrightarrow{b}\,\,\overrightarrow{b}\,+\,\overrightarrow{c}\,\overrightarrow{c}\,+\,\overrightarrow{a}]\] is equal to:

    A)  \[[\overrightarrow{a}\,\,\overrightarrow{b}\,\,\overrightarrow{c}]\]                   

    B)                         \[0\]

    C)                         \[2[\overrightarrow{a}\,\,\overrightarrow{b}\,\,\overrightarrow{c}]\]                 

    D)                         \[{{[\overrightarrow{a}\,\,\overrightarrow{b}\,\,\overrightarrow{c}]}^{2}}\]

    E)                         \[(\overrightarrow{a}\,\times \,\overrightarrow{b})\times \,\,\overrightarrow{c}\]

    Correct Answer: C

    Solution :

    \[[\overrightarrow{a}+\overrightarrow{b}\overrightarrow{b}+\overrightarrow{c}\overrightarrow{c}+\overrightarrow{a}]\] \[\left[ (\overrightarrow{a}+\overrightarrow{b})\times (\overrightarrow{b}+\overrightarrow{c}) \right].(\overrightarrow{c}+\overrightarrow{a})\] \[=[\overrightarrow{a}\times \overrightarrow{b}+\overrightarrow{a}\times \overrightarrow{c}+\overrightarrow{b}\times \overrightarrow{b}+\overrightarrow{b}\times \overrightarrow{c}].(\overrightarrow{c}+\overrightarrow{a})\] \[=[\overrightarrow{a}\,\,\,\overrightarrow{b}\,\,\,\,\overrightarrow{c}]+[\overrightarrow{a}\,\,\overrightarrow{b}\,\,\overrightarrow{c}]\] \[=2[\overrightarrow{a}\,\,\,\overrightarrow{b}\,\,\,\,\overrightarrow{c}]\]


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