There are infinitely many possible answers. One of these is a icosahedron.
Because it hasn't any straight lines that meet each other at an angle and it's circular in shape
A square and rectangle both have congruent triangles in them.
A football is circular, or rather spherical, because no other shape will roll in any direction.
When triangles have the same shape but not necessarily the same size, they are called similar triangles. This means that their corresponding angles are equal, and their corresponding sides are in proportion to each other. Similar triangles can be scaled versions of one another.
the shape that can make two smaller triangles is parallelogram.
The answer depends on the shape. There are different formulae for triangles, quadrilaterals and other polygons. Since you have not bothered to provide any information on the shape,I cannot provide a more useful answer.The answer depends on the shape. There are different formulae for triangles, quadrilaterals and other polygons. Since you have not bothered to provide any information on the shape,I cannot provide a more useful answer.The answer depends on the shape. There are different formulae for triangles, quadrilaterals and other polygons. Since you have not bothered to provide any information on the shape,I cannot provide a more useful answer.The answer depends on the shape. There are different formulae for triangles, quadrilaterals and other polygons. Since you have not bothered to provide any information on the shape,I cannot provide a more useful answer.
the bottom one is a square and the other 4 are triangles
The simplest such shape is PYRAMID.
congruent triangles
There can be no closed 3D shape with only one square and 3 triangles.
Because triangles are stable shapes.
A nine sided shape has 7 triangles