No.
It can be but need not be.
180 degrees
Triangles are one type of polygon
half of base times altitude.
trianle have no faces, because it is 2D figure.
No, they are the faces of the polyhedron.
The definition of polyhedron. If it was not faceted it would not be a polyhedron.
This is the formula to find the hypotenuse of a right angle trianle
yes it is a polyhedron
They are the faces of the polyhedron.
No, a cubiod is not a polyhedron but a cuboid is.
180 degrees