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What is scalar product of a=2i-3j, b=6i+4j?

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chezmena | Student, College Freshman

Posted December 3, 2011 at 11:54 PM via web

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What is scalar product of a=2i-3j, b=6i+4j?

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sciencesolve | Teacher | (Level 3) Educator Emeritus

Posted December 4, 2011 at 12:08 AM (Answer #1)

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Remember the formula of dot scalar product:

`bar a` * `barb` = |bara|*|barb|*cos theta

theta is the angle between bara and barb

|a| is the magnitude of the vector a: bara = sqrt(2^2 + (-3)^2)

bara = sqrt 13

|b| is the magnitude of the vector b:

 `barb = sqrt(6^2 + 4^2)` `bara = sqrt 52 = 2sqrt13`

`` `bara*barb = (sqrt13)*(2sqrt13) cos theta`

The scalar product is `bara*barb`  =26 cos `theta`  .

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