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Math Help - Question about simple multiplication

  1. #1
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    Question about simple multiplication

    Sorry about all my threads, but hope you guys can help me once again.
    Just a simple question.

    f(x) = a + bcos2x
    f(0) = a + bcos2(0) = -1

    Now this is where I'm slightly confused. "Anything multiplied by 0 is 0", right, and because b is multiplied to cos2(0), then surely that removes b and you get:

    f(0) = a + b(0)
    f(0) = a = -1

    But, according to the textbook, it's not. They say its:

    f(0) = a + b = -1

    Why?
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  2. #2
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    Re: Question about simple multiplication

    Quote Originally Posted by yorkey View Post
    Sorry about all my threads, but hope you guys can help me once again.
    Just a simple question.

    f(x) = a + bcos2x
    f(0) = a + bcos2(0) = -1

    Now this is where I'm slightly confused. "Anything multiplied by 0 is 0", right, and because b is multiplied to cos2(0), then surely that removes b and you get:

    f(0) = a + b(0)
    f(0) = a = -1

    But, according to the textbook, it's not. They say its:

    f(0) = a + b = -1

    Why?
    cos(2x0) = cos(0) = 1.
    Thanks from yorkey
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  3. #3
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    Re: Question about simple multiplication

    Quote Originally Posted by yorkey View Post
    Now this is where I'm slightly confused. "Anything multiplied by 0 is 0", right, and because b is multiplied to cos2(0)
    But \cos(2\cdot0)=\cos(0)=1, not 0. I am sure you don't think that \cos(0) = {\cos}\cdot0=0.
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  4. #4
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    Re: Question about simple multiplication

    Oh. Actually I did think that cos(0) = 0. I... didn't think.

    Sorry for the trouble! Thanks again.
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