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Math Help - magnitude of velicity vector

  1. #1
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    magnitude of velicity vector

    I have a velocity vector:

    6 t cos(t^2) i - 6 t sin (t^2) j and I need to get the magnitude of this. I put it under the square root sign while squaring both terms and adding them together. The answer is 6 l t l but I can not figure out why!!!! Anyone able to explain would be very much appreciated. Frostking
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  2. #2
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    Quote Originally Posted by Frostking View Post
    I have a velocity vector:

    6 t cos(t^2) i - 6 t sin (t^2) j and I need to get the magnitude of this. I put it under the square root sign while squaring both terms and adding them together. The answer is 6 l t l but I can not figure out why!!!! Anyone able to explain would be very much appreciated. Frostking
    So you got
    \sqrt{36 t^2 cos^2(t^2)+ 36 t^2 sin^2(t^2)}
    = \sqrt{36 t^2 (cos^2(t^2+ sin^2(t^2))}
    What is sin^2(t^2)+ cos^2(t^2)?

    What is \sqrt{36}

    What is \sqrt{t^2}?

    Be careful with that last one! Think about t= -2.
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