# Thread: Relation between the diagonals of a regular octagon from a point

1. ## Relation between the diagonals of a regular octagon from a point

I'm trying to figure out the relation between the diagonals of a regular octagon from a point. Can any one help me out?
In the attached image, please help me to find out the relation between the lengths of a,b,c with respect to diameter d of the circle to which it's inscribed

2. Chord if you go to this webpage you will find the formula for finding the length of a chord of a circle in terms of its central angle and radius: $a=2R\sin\left(\frac{\theta}{2}\right)$.

Now for an octagon the sides and diagonals are subtended by
$\frac{\pi}{4},~\frac{\pi}{2},~\frac{3\pi}{4},~\&~\ pi$.

That will give the four length you need.