vertical angle; vertex angle
Geometry term for the angle at the vertex of a shape, especially the apex of an isosceles triangle or the vertex of a cone.
Find the vertex angle of the isosceles triangle.
円錐の頂角が小さいほど、先端が鋭くなる。
The smaller the vertical angle of a cone, the sharper its tip.
Compound of 頂 (vertex, top) and 角 (angle). The reading ちょうかく follows standard on'yomi.