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A triangle has three angles.
A polygon with 6 sides is an hexagon
Yes a square is a regular 4 sided polygon
any ellipse, any pie-wedge of a circle, etc.
A trapezoid is a 4 sided polygon belonging to the class of 4 sided quadrilaterals
A four sided polygon can be a square, a parallelogram, a rectangle, a rhombus or a kite.
It could be any number of sides, poly is the Greek word for many...
its named that because it is on the rivers side.