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: