No, neither.
A quadrangle is a closed figure that has the following attributes: 2-dimensional, 4 vertexes, 4 sides, and 4 angle
All angles are made up when two lines or sides vertexes or intersection points, I think.
two
Decagon
No.
A CIRCLE OR AN OVAL
It is simply a right angle triangle but if the sides were the same then it is an isoceles right angle triangle
In plane geometry, a shape with four sides, two of which are parallel and have the same length, cannot have a reflex angle.
cube
a triangle with two sides the same length and no right angle
An octahedron is an eight sided polyhedron. It has eight sides or faces, 12 edges, and six vertexes. Please see the Related Link below for more information and a picture.
A pyramid is a solid with a (convex) polygonal base and triangular sides all terminating in the same point. As such the number of "corners" (topologists call them vertexes) is one more than the number of vertexes of the base. A "square pyramid" (such as those famous structures in Giza, Egypt, has five vertexes. A tetrahedron is also a pyramid but one that has only 4 vertexes (the fewest of all the pyramidal shapes). 3