The tomahawk is a geometric shape with an unknown inventor. The basic shape is constructible with ruler and compass, but is able to do much more than is possible with the straight-edge and compass alone, primarily due to the ability of the tomahawk to be lined up with figures and make comparisons. It is possible to trisect an angle with the tomahawk by lining up one ray of the angle with point R in the picture, letting the vertex lie on SV, and letting the other ray tangent to semicircle SDU. Then, by congruent triangles BRS, BTS, and BTD, BS will trisect the angle.