TRIANGLES
they are cirques
Cirques
Three-sided valleys, often referred to as "V-shaped valleys," are geological formations typically created by the erosive action of rivers or streams. They feature steep sides and a narrow bottom, resembling the letter "V" in cross-section. These valleys are commonly found in mountainous or hilly regions, where the rapid flow of water cuts into the landscape, deepening the valley over time. The shape and formation of three-sided valleys are indicative of youthful river systems still actively carving into the terrain.
a deep, steep-sided, narrow river valley
The name of the angle which has three sided polygon called Triangle.
It is called a triangle.
It is called a triangle. three-sided polygon is called a triangle, from the Greek word "tri" meaning "three" as in tricycle, or tripod. from : espi
triangle
=Pyramid=
A three-sided, two-dimensional polygon is called a "triangle".
triangle
Octahedron.
A triangle