Tetrahedra in the solid geometry is called a polyhedron composed of four triangular faces. The tetrahedron has 6 edges and 4 faces and vertices.
If all the faces of the tetrahedron are right triangles, the tetrahedron, and he called right.
Total surface area of any polyhedron including a tetrahedron can be calculated from the area of its faces.
To find the total surface area of the tetrahedron, it is necessary to calculate the triangle area of his face.
If the triangle is equilateral, then its area is
S = 3 * 4 / a ?, where a -? A rib of the tetrahedron,
then the surface area of the tetrahedron is given by
S =? 3 * a ?.
If the tetrahedron is rectangular, ie.e. all of the plane angles at one of its vertices are straight, the area of three of its faces are right triangles can be calculated by the formula
S = a * b * 1/2,
S = a * c * 1/2,
S = b * c * 1/2,
the third face area can be calculated by one of the general formulas for the triangles, such as the Heron's formula
S = (p * (p - d) * (p - e) * (p - f))?, Where p = (d + e + f) / 2 - half-perimeter of the triangle.
In general, any tetrahedron area can be calculated by using Heron's formula for calculating the area of each of its faces.