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Math Help - Integral containing two separate sin functions

  1. #1
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    Integral containing two separate sin functions

    Hey all, my integration is a bit rusty so I'm having trouble with integrating a function thats something like:

    sin(yx)sin(zx)dx

    How would I go about a problem like that?
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  2. #2
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    Quote Originally Posted by blorpinbloo View Post
    Hey all, my integration is a bit rusty so I'm having trouble with integrating a function thats something like:

    sin(yx)sin(zx)dx

    How would I go about a problem like that?
    Use the following trigonometric identity:

    sin(a)sin(b)=\frac{1}{2}[cos(a-b)-cos(a+b)]
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  3. #3
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    Quote Originally Posted by blorpinbloo View Post
    Hey all, my integration is a bit rusty so I'm having trouble with integrating a function thats something like:

    sin(yx)sin(zx)dx

    How would I go about a problem like that?
    It needs to be asked if y and/or z are functions of x or if they are independent of x?
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  4. #4
    Junior Member slider142's Avatar
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    Assuming y and z are not functions of x, the integral is independent of these variables and y and z may be treated as constants. Then integration by parts (applied twice to get a multiple of the original integrand) makes short work of this integral.
    Otherwise, you need to know those functions of x.
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