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Thread: Need help!

  1. #1
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    Default Need help!

    Ok

    The question is

    ' Functions with the property demonstrated by part 1) have a special name in mathematics, what is it?'

    Part 1 is where I multiply various sines and cosines together ex:

    sinxcosx, cosxcosy, sinxsiny to put it frankly random configurations of sin and cos values for which i had a table of
    The answers i got were all approximately 0 (all very close to zero)
    so the question im asking would be what are those numbers called when multiplied and summed up approximate to 0?

    Thanks
    This is final year automotive engineering shit by the way
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  2. #2
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    So you're saying you were asked to combine sines and cosines in various ways, all of which yielded zero everywhere?

    In that case the term you're looking for is perhaps "constant". The functions are all constant.

    In general combinations of sines and cosines may be termed "trigonometric functions", although the most interesting ones aren't constant .

    Quote Quote
    so the question im asking would be what are those numbers called when multiplied and summed up approximate to 0?
    No that's not your question. If you think this is the core of the problem you really don't understand what you're doing. You're dealing with functions, not numbers. There's an important distinction there.

    I could probably be more helpful if I got to see part 1. It's not overly clear to me what this property might be.
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  3. #3
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    I'm suspired, BB, there's not much more you need to see. Sine and cosine are orthogonal. He's in an engineering class, so they should have a notion of orthogonality from signal processing.

    Two functions f(x) and g(x) are orthogonal if the integral of [f(x)g(x) dx] over some specified range (often ±Infinity) is 0.
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    Oh right, that makes sense.

    OP doesn't even mention integrals though...

    Quote Originally Posted by MacMan View Post
    Two functions f(x) and g(x) are orthogonal if the integral of [f(x)g(x) dx] over some specified range (often ±Infinity) is 0.
    sin*cos isn't integrable over the whole of R, however. The interval is more likely [0, 2*pi].
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  5. #5
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    Excellente. Orthogonal. Even though I swear i heard that being associated with something else. And you're right it is about signal processing in the 1st, 2nd, 3rd...harmonic.

    I'll look into this orthogonal thing. And TheBB I am aware of the fact that they are trignometric functions I was just unsure as to how to frame the question to a group of people who're mostly non-engineering students
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    Quote Originally Posted by Diaboli View Post
    how to frame the question to a group of people who're mostly non-engineering students
    Heck, I'm a math student. Bring it on. The more precise the question, the better I can answer.
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