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Math Help - Confused on multiplication order...

  1. #1
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    Confused on multiplication order...

    I have a conflict between my teacher's method of teaching and how the book explains how to do this certain problem...

    " Translate by (-2,3) and then scale the x-cord by .8 and the y-cord by 1.2. "

    I assumed since it asked to translate the Identity matrix by (-2,3) first, I was suppose to do that and then scale. Yet.. my teacher told us we first must scale then translate. This is confusing the heck out of me. I understand they are not commutative in the sense that TD =/= DT.

    Any help would be awesome.
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  2. #2
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    Quote Originally Posted by ARR0624 View Post
    I have a conflict between my teacher's method of teaching and how the book explains how to do this certain problem...

    " Translate by (-2,3) and then scale the x-cord by .8 and the y-cord by 1.2. "

    I assumed since it asked to translate the Identity matrix by (-2,3) first, I was suppose to do that and then scale. Yet.. my teacher told us we first must scale then translate. This is confusing the heck out of me. I understand they are not commutative in the sense that TD =/= DT.

    Any help would be awesome.
    Personally, with the way the question is worded, I agree with you. If that is what your teacher wanted, this is badly worded.

    -Dan
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