Thread: Circle geometry + trig View Single Post

## Circle geometry + trig

In one of my books there is a question:

"Problem: What is the trigonometric relationship between the length of the chord and the angle subtended at the centre?"
$$\theta$$ is the angle subtended at the centre.

Next to it is simply written:

$$2r \sin(\frac{\theta}{2}) = l$$

I'm sure I wrote that; but I can't remember proving it.

Can anyone help?