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Math

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If a = 3i + 2j - k and b = -2i + j calculate each magnitude.

a) a + b
I got sqrt3, but the answer at the back of the book says sqrt11.

2) If D(3,4,5) and E(-2,1,5) are points in space calculate each expression and state what it represents.
|OD|

can you please do those and explain steps.

  • Math -

    a + b = (3-2) i +(2+1) j +(-1+0) k
    = 1 i + 3 j -1 k
    sqrt (1^1 + 3^2 + (-1)^2 )
    sqrt ( 1 + 9 + 1)
    sqrt (11)
    The book wins again :)

  • Math -

    Wow I accidentally put a - in front of 2 and ended up with -1. Thanks!

  • Math -

    2) If D(3,4,5) and E(-2,1,5) are points in space calculate each expression and state what it represents.
    |OD|
    -------------------
    I assume 0 is the origin (0,0,0)
    so OD = (3-0)i + (4-0) j + (5-0) k
    and
    |OD| = sqrt (3^2 + 4^2 + 5^2)
    =sqrt (9 + 16 + 25)
    = sqrt(50)
    = 5 sqrt(2)

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