square
Trusses are structural elements made up of a series of interconnected triangles. This design helps to distribute loads efficiently and increase stability in buildings and bridges.
An hexagon is made up out of 4 triangles
The Great Pyramids at Giza are, but the Meso-Americans were truncated.
27, but you will have to prove it.
Israel
An octagon is made up from six triangles each containing 180 degrees.
a geometric shape made up of 20 triangles. :)
geodesic
Assuming ALL 22 triangles are congruent, this would be a 22-gon, also known as an icositedigon
It would depend on the triangles, but assuming they were equilateral or isosceles, a trapezoid if alternated in a line.
rectangular pyramid
The Triforce in Zelda games!