Chapter 18: Plane Figures

Lesson 1: Polygons. Objective: To identify polygons and to classify polygons as regular or not regular.

Lesson 2: Classify Triangles. Objective: to classify triangles by the lengths of their sides and by the measures of their angles.

Lesson 3: Classify Quadrilaterals. Objective: To identify and classify quadrilaterals.

Lesson 4: Problem Solving Strategy: Draw a Diagram. Objective: To use the strategy *Draw a diagram* to solve problems.

Lesson 5: Circles. Objective: To draw and identify the parts of circles.

Vocabulary: right angle, acute angle, obtuse angle, square, rectangle, polygon, triangle, quadrilateral, pentagon, hexagon, octagon, regular polygon, equilateral triangle, isosceles triangle, scalene triangle, trapezoid, Venn diagram, circle, center, chord, diameter, radius, compass

**right angle: **an angle that measures 90 degrees

**acute angle: **an angle that measures greater than 0 degrees but less than 90 degrees

**obtuse angle: **an angle that measures greater than 90 degrees but less than 180 degrees

**square: **a quadrilateral with 4 equal sides and 4 right angles

**rectangle: **a quadrilateral with opposite sides that are equal, and 4 right angles

**polygon: **a closed plane figure with straight sides

**triangle:** a polygon with 3 sides

**quadrilateral: **a polygon with 4 sides

**pentagon: **a polygon with 5 sides

**hexagon: **a polygon with 6 sides

**octagon: **a polygon with 8 sides

**regular polygon: **a polygon in which all sides have equal length and all angles have equal measure

**equilateral triangle: **a triangle with 3 equal sides

**isosceles triangle: **a triangle with 2 equal sides

**scalene triangle: **a triangle with no equal sides

**trapezoid: **a quadrilateral with exactly one pair of parallel sides

**Venn Diagram: **a diagram that shows relationships among sets of things

**circle: **a closed plane figure made up of points that are the same distance from the center

**center: **a point inside a circle that is the same distance from each point on the circle

**chord: **a line segment that has its endpoints on the circle

**diameter: **a chord that passes through the center of the circle

**radius: **a line segment with one endpoint at the center of the circle and the other endpoint on the circle

**compass: **a tool used to construct circles

Our textbook website: www.harcourtschool.com

Some good practice websites:

http://www.gamequarium.com/placevalue.html

http://www.softschools.com/math/games/

www.multiplication.com

www.funbrain.com