Notice, since polygons are Circles are not polygons. Polygon: a closed figure formed by three or more line segments. Notice, since polygons are Circles are not polygons. Hexagon Quadrilateral Triangle Pentagon

Triangle: a polygon with three sides Classified by sides and angles

Congruent sides have the same length Congruent sides have the same length. You can classify a triangle by the number of congruent sides it has.

Scalene triangle: no congruent sides.

indicate congruent sides Isosceles triangle: at least two congruent sides. Tick marks are used to indicate congruent sides

All equilateral triangles are also isosceles triangles. three congruent sides. All equilateral triangles are also isosceles triangles.

You can also classify a triangle by its angle measures.

A square indicates the 90° angle in the right triangle. one right angle A square indicates the 90° angle in the right triangle.

Acute triangle: three acute angles (angles of less than 90°)

Obtuse triangle: One obtuse angle (angle greater than 90°)

Quadrilateral: a polygon with four sides Parallelogram: a quadrilateral with both pairs of opposite sides parallel.

Rectangle: a parallelogram with four right angles Square: a rectangle with four congruent sides

What is the area of this rectangle?

Length x Width or Base x Height

So how big is this rectangle? Correct 48 square units So how big is this rectangle?

A parallelogram is formed which has the same area as the rectangle. If, with the help of our 16th President, we chop a piece off the rectangle… Then move it to the other side…

Always look for the 90° square. And since it has the same area, we can use the same formula. base x height Always look for the 90° square.

Don’t worry about the length of the sides. That is called “slant height.”

Sometimes you will see the base and height connected like this.

b x h 6 x 5 15 30 units units one-half base times height. then the area of a triangle is… If the area of a rectangle is b x h, and a triangle is half a rectangle,

Does that only work with right triangles? NO

move it to form a rectangle. Copy this scalene triangle, rotate it 180 degrees, chop it at the vertex, move it to form a rectangle. Copy this scalene triangle,

Area = ½ bh 8m 10m Area = (½)(10)(8) = 40m2

Trapezoid is related to trapeze. a circus elephant stands on, but this polygon’s name This may look like the stool comes from the top of the circus.

The height is found between them. Trapezoids have one pair base one base two The height is found between them. Trapezoids have one pair of parallel lines called bases.

the average of the bases b1 + b2 2 Area = h the average of the bases x the height