The figure shows two semicircles and a quarter of a circle. Find the area of the shaded region. Use . for . Be sure to include the formula and all of the steps you took to solve the problem! Organize your work! A triangle is a figure with three sides and three angles. The symbol for triangle is . Every triangle has at last two acute angles. One way to classify triangles is by using the third angle. Another way to classify triangles is by their sides. Sides with the same length are congruent segments. The figure below is a quadrilateral, since it has four sides and four angles. A polygon is a simple, closed figure formed by three or more straight line segments. A simple figure does not have lines that cross each other. You have drawn a closed figured when your pencil ends up where it started. A polygon can by classified by the number of sides it has. An equilateral polygon has all sides congruent. A polygon is equiangular if al of its angles are congruent. A regular polygon is equilateral and equiangular, with all sides and all angles congruent. Determine whether each figure is a polygon. If it is, classify the polygon and state whether it is regular. If it is not a polygon, explain why. Determine whether each figure is a polygon. If it is, classify the polygon and state whether it is regular. If it is not a polygon, explain why.