Trigonometric constants expressed in real radicals in a regular polygon: a vertex, an edge center containing that vertex, and the polygon center. An "n"-gon can be divided into 2"n" right triangles with angles of , 90 − , 90} degrees, for "n" in 3, 4, 5, … Constructibility of 3, 4, 5, and 15-sided polygons are the basis, and angle bisectors allow multiples of two to also be derived. In degree format, sin and cos of 0, 30, 45, 60, and 90 can be calculated from their right angled triangles, using the Pythagorean theorem. In radian format, sin and cos of / 2 can be expressed
120-gon 120-gon In geometry, a 120-gon is a polygon with 120 sides. The sum of any 120-gon's interior angles is 21240 degrees. Alternative names include dodecacontagon and hecatonicosagon. A "regular 120-gon" is represented by Schläfli symbol {120} and also can be constructed as a truncated hexacontagon, t{60}, or a twice-truncated triacontagon, tt{30}, or a thrice-truncated pentadecagon, ttt{15}. One interior angle in a regular 120-gon is 177°, meaning that one exterior angle would be 3°. The area of a regular 120-gon is (with ) and its inradius is The circumradius of a regular 120-gon is This means that the trigonometric functions of