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# integration watch

1. integrate between L and -L :
sin(m.pi.x/L)sin(n.pi.x/L)
to show it = 0

i can do it for cos because wen u integrate cos u get sin and all multiples of pi are 0. but for cos the multiples of pi are eitha 1 or -1

can someone show me explicitly how to do this
2. Could you just say that because you're integrating between -L and L, and as sin is an odd function, that the integral must be zero as the positive portion will exactly cancel the negative one?
3. unfortunately not ive actually got to do the integral
4. couldnt do it but heres it in LaTeX form.. I'm practicing
Attached Images

5. Expand Cos(A+B) and Cos(A-B) to find an expression for Sin(A)Sin(B), then apply this to your question.

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Updated: January 27, 2005
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