# What is the solution to ΣΣ(sinx)(cosx)?

1. Dec 4, 2007

### abhaiitg

what is the solution to this ?
∞∞
ΣΣ(sinx)(cosx)=??
00

2. Dec 4, 2007

### Xevarion

Your question isn't clear. What variables are you summing over? And where do those appear in the summand?

3. Dec 6, 2007

### colby2152

Are one of the trig functions supposed to be a function of y?

4. Dec 6, 2007

### HallsofIvy

Staff Emeritus
Since there was no y mentioned in the entire post, apparently not! But Xevarion's point is more than that. Typically "x" (or "y") in a function represents a continuous variable- but the sums must be over discrete indicies.

Perhaps it was
$$\sum_{n= 0}^\infty \sum_{m= 0}^\infty sin(n)cos(m)$$
that was intended. But the only way we will know for sure is if abhaaiitg tells us!

5. Dec 7, 2007

### abhaiitg

yeah it was as u think

6. Dec 7, 2007

### Xevarion

That sum doesn't converge. There are arbitrarily large $m, n$ with $|\sin(n)\sin(m)|$ close to 1.