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chrisplusian

  • one year ago

linear algebra question... see attachment

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  1. chrisplusian
    • one year ago
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  2. chrisplusian
    • one year ago
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    Is there a way to show this using linear algebra? I have expanded it and shown through the multiplication and trig identities that it is true but it required a whole page of work, I am thinking there may be an easier way?

  3. rock_mit182
    • one year ago
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    I guess you can use determinants

  4. rock_mit182
    • one year ago
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    since |A| = 1

  5. rock_mit182
    • one year ago
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    REMEMber that Cos^2 + sin^2 = 1 by trig identities

  6. chrisplusian
    • one year ago
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    @rock_mit182 a more useful identity in this case is (cos(x))^2-(sin(x))^2 = cos(2x) but my professor has pointed out that I am doing great on quizzes and tests but I am using "old" methods and need to depend on properties of linear algebra to simplify matters. So in this problem I have come to the solution, but through actually multiplying them out, and using trig identities. My question is not how to obtain an answer, but rather is there a way to do this VIA linear algebra properties that does not require me to expand the matrices using multiplication and using trig identities to verify the truth of the statement?

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