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Math Help - Algebraic Vectors 2

  1. #1
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    Algebraic Vectors 2

    Given a and b unit vectors, if |a+b|=sqrt3, determine (2a-5b) . (b+3a)

    Just wanted to know if someone could check if I have the correct solution and answer to the q above.

    -13a.b+6|a|^2-5|b|^2
    =-13(0.5)+6(1)^2-5(1)^2
    =-5.5

    I got 0.5 above for a.b dot product like this:

    |a+b|=sqrt3^2
    |a+b|^2=(a+b)(a+b)
    3=(a^2)+2a.b+b^2
    0.5=a.b
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  2. #2
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    Quote Originally Posted by skeske1234 View Post
    Given a and b unit vectors, if |a+b|=sqrt3, determine (2a-5b) . (b+3a)
    -13a.b+6|a|^2-5|b|^2
    =-13(0.5)+6(1)^2-5(1)^2
    =-5.5
    I got 0.5 above for a.b dot product like this:
    Correct.
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