pentagon
triangle
A shape with five sides, where all interior angles are less than 180 degrees, is called a convex pentagon. In a convex pentagon, each interior angle is greater than 0 degrees and less than 180 degrees, ensuring the shape bulges outward rather than inward. This property distinguishes it from concave polygons, where at least one interior angle exceeds 180 degrees.
A triangle or a circle.
You cannot answer this with a normal shape. Any shape given would have less an infinite sides. The exception to this would BE the shape with infinite sides and therefore by the same token, an infinite perimeter. So, the answer would be a "Fractal"
It has less than three sides.
The pentagon satisfies those criteria precisely.
triangular pyramid-4 equal faces
Common shapes with less than 4 sides are triangles and circles ( but the circle has no straight sides).
Pentagon.
a pentagon is a polygon with 5 sides not less or more.
A polygon with 4 sides has 4 angles. All polyhedra have at least 4 vertices so I cannot think of any shape that meets the requirements.
A right angle triangle