Question 167
Using eight isosceles right-angled triangles we assemble a regular octagon with an octagonal hole, as shown in the figure. The side length of the regular octagon equals $1$ cm. How many centimetres is the side length of the octagonal hole?
(A) $\frac{\sqrt{2}}{2}$
(B) $\frac{1}{2}$
(C) $2 - \sqrt{2}$
(D) $\sqrt{2} - 1$
(E) $\sqrt{3}$
(A) $\frac{\sqrt{2}}{2}$
(B) $\frac{1}{2}$
(C) $2 - \sqrt{2}$
(D) $\sqrt{2} - 1$
(E) $\sqrt{3}$