octagon with radius of 1.4m calculate the width of each side

Consider the octagon to be made up of 8 triangles each of which look like the image below:

Angle β is (180-45)/2 = 67.5°

Use the sin rule to get s

s/sin(45°) = 1.4/sin(67.5°)

$${\mathtt{s}} = {\frac{{\mathtt{1.4}}{\mathtt{\,\times\,}}\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}{\left({\mathtt{45}}^\circ\right)}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}{\left({\mathtt{67.5}}^\circ\right)}}} \Rightarrow {\mathtt{s}} = {\mathtt{1.071\: \!513\: \!610\: \!623\: \!269\: \!6}}$$  

s ≈ 1.07m