Odd and Even Function ConstructionsDate: 06/08/98 at 20:35:00 From: C. Brinson Subject: Odd and even function constructions If f is an odd function and g is an even function, how do we go about combining the two in various constructions (such as adding the two, multiplying the two, composing one with the other, etc.)? How do we know if the "new" function is even or odd? I know there is an easy way to figure this out, like substituting x with (-x), but I'm stuck and it's been a while since I've had to think about such things. Thanks. C. Brinson Date: 06/16/98 at 21:50:14 From: Doctor Schwa Subject: Re: Odd and even function constructions An odd function is one where f(-x) = -f(x), and an even function is one where g(-x) = g(x). That is, x^(odd power) is an example of an odd function, and x^(even power) is an example of an even function. So for example, if you multiply an odd and an even function, you can tell from the x^(power) example that the result will be odd, because the powers add. You can prove it in general by taking fg(-x) = f(-x)g(-x) = -f(x) g(x) = -(fg(x)) When you add an odd and an even function, in general you'll get a function that's neither odd nor even. In fact any function h(x) can be written as a sum of an odd and even part, by taking f(x) = (h(x) - h(-x))/2 as the odd part, and g(x) = (h(x) + h(-x))/2 for the even part. -Doctor Schwa, The Math Forum http://mathforum.org/dr.math/ |
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