As you probably know the beat frequency of the combination of two sign waves is their greatest common factor.

so naturally I wondered what the beat frequency of an irrational ratio would be.

I found a way of finding a wave that perfectly fit visually but I don't know how to simplify this equation.

sin(ax)sin(bx) + cos(ax)cos(bx) = cos(2cx)

what is the value of c?

## Simplifying a Trigonometric Expression

**Moderators:** gmalivuk, Moderators General, Prelates

### Re: Simplifying a Trigonometric Expression

Have you ever seen the identity [imath]\cos(a-b)=\cos(a)\cos(b) +\sin(a)\sin(b)[/imath]?

(See here for reference).

(See here for reference).

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