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# Need help with this limit. watch

1. Hello I'm currently trying to find the Riemann integral of sinx from 0 to a and have arrived at this limit.

which I have no idea how to evaluate.

Any idea?

Thanks.
2. What is the question? Finding this integral is much easier if you can use theorems like the fundamental theorem of calculus.
3. (Original post by james22)
What is the question? Finding this integral is much easier if you can use theorems like the fundamental theorem of calculus.
By dissecting sinx between 0 and a into n parts find the riemann sum and thus the riemann integral for sinx between 0 and a.

I may be having some luck finding a way to do this I'm trying now.
4. (Original post by poorform)
By dissecting sinx between 0 and a into n parts find the riemann sum and thus the riemann integral for sinx between 0 and a.

I may be having some luck finding a way to do this I'm trying now.
You can write it as the sum of sin (or cos) terms, and use de moivre's theorem.
5. (Original post by james22)
You can write it as the sum of sin (or cos) terms, and use de moivre's theorem.
I tried that and I made a complete mess of it all. could you help anymore with some tips please.
6. (Original post by poorform)
I tried that and I made a complete mess of it all. could you help anymore with some tips please.
It should work, what did you try?

Can you write sin(x)sin(y) as the sum of 2 trig functions?

Can you apply de moivre's theorem to sums of trig functions?
7. (Original post by james22)
It should work, what did you try?

Can you write sin(x)sin(y) as the sum of 2 trig functions?

Can you apply de moivre's theorem to sums of trig functions?
I have figured it out now.

Thanks for the help.

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