As 40 = 23 × 5, a regular tetracontagon is constructible using a compass and straightedge.[3] As a truncated icosagon, it can be constructed by an edge-bisection of a regular icosagon. This means that the values of sin ⁡ π 40 {\displaystyle \sin {\frac {\pi }{40}}} and cos ⁡ π 40 {\displaystyle \cos {\frac {\pi }{40}}} may be expressed in radicals as follows: