Length of prism * perimeter of triangular face.
Triangular Prism, Triangular Pyramid.
A cuboid prism has no triangular faces
A prism has a variety of bases but the sides are always parallelograms. A triangular prism has a triangle as the two bases and parallelograms as lateral sides. A pyramid has a variety of bases but the sides are triangles.
The lateral faces of a prism - pentagonal or other - are rectangular.
It is a triangular prism
both have lateral face shapes that are riangles
The lateral faces of a prism are either squares, rectangles or parallelograms. If the prism is oblique then the faces must be parallelograms and not rectangles or squares.
A right triangular prism has two identical faces. Two faces may or may not be identical in an oblique prism, in which the lateral edges are not perpendicular to the bases.
The lateral area of a triangular prism is found by computing the perimeter of the triangular base (sum of the three sides) and multiplying it by the height of the prism. If the triangular base has sides of length s1, s2, and s3, and the height of the prism is h, then each lateral face of the prism would be a rectangle. The area of one face of the prism would be (s1 x h), the area of the second face of the prism would be (s2 x h), and the area of the third face of the prism would be (s3 x h). So the three lateral faces would have a total area of (s1 x h) + (s2 x h) + (s3 x h), or equivalently (s1 + s2 + s3) x h; i.e., (the perimeter of the triangular base) x (the height of the prism).