How do you find the area of a 3 dimensional triangle?

Please note that all triangles are 2-dimensional figures.
There can be 3-dimensional triangles. Thus there is no question of finding area of a
three dimensional triangle.

However we do have
3-dimensional solids, that have triangle shaped faces. For example, a solid called
tetrahedron having four vertexes (extreme points) has four triangular faces. A
Triangular prism has two triangular faces and three rectangular faces. A square pyramid
has a square base and four triangular sides.

We can find
areas of triangular or other shaped surfaces of such solids by working out areas of each
face separately and then adding them together.