A right triangle has one right angle.
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A plane figure is any closed, two-dimensional shape.
A square is a quadrilateral with four congruent (equal length) sides and four right angles.
A polygon is a closed plane figure composed of at least three line segments that do not cross. A plane figure is any closed, two-dimensional shape.
A rectangle is a quadrilateral with four right angles.
decagon is a ten-sided polygon. (b)