Polygons and Lines of Symmetry

Unit 8 Review

Let's review the content covered in Unit 8 to be prepared to take the assessment!

Let's review what a polygon is!

A shape that MUST include the following:

• at least 3 straight sides

• all sides are closed

Multiple Choice

Which of the following is NOT a polygon?

Attributes of Polygons

We have talked about two main types of polygons during this unit:

- Triangles
- Quadrilaterals

What are some attributes that differ between the two types?

Multiple Select

Which of the following triangles are RIGHT triangles?

Types of Triangles

There are 4 different types of triangles:


1. Equilateral triangle - all sides are equal, all angles are equal, 3 lines of symmetry
2. Right triangle - 2 sides are equal; 1 angle is 90 degrees; 1 line of symmetry
3. Scalene triangle - no sides or angles are equal, no lines of symmetry
4. Isosceles triangle - 2 sides are equal; 2 angles are equal; 1 line of symmetry

Multiple Choice

Which of the following are TRUE about triangles?

• A right triangle never has a line of symmetry.

• A right triangle sometimes has a line of symmetry.

• A right triangle always has a line of symmetry.

• If a triangle has a line of symmetry then it is a right triangle.

Types of Quadrilaterals

Quadrilaterals are 4 sided polygons:
1. Square - sides are all equal, each angle is 90 degrees
2. Rectangle - 2 pairs of parallel sides; each angle is 90 degrees
3. Trapezoid - 1 pair of parallel sides
4. Rhombus - all sides are equal, 2 pairs of parallel sides
5. Parallelogram - 2 pairs of parallel sides that are equal

Open Ended

Is this shape a rhombus? Is it a rectangle? Explain how you know.

Open Ended

Is this shape a rhombus? Is it a square? Explain how you know.

Let's review the types of angles!

There are 3 types of angles! We all know and love them. Say them with me!

- Acute angle: less than 90 degrees
- Right angle: exactly 90 degrees
- Obtuse angle: greater than 90 degrees

Multiple Select

Which of the following statements are true?

• Some rhombuses have an obtuse angle.

• All rectangles have a right angle.

• All rhombuses have a right angle.

• Lines containing opposite sides of rectangles are parallel.

Lines of Symmetry

A line of symmetry is the line that divides a shape (polygon) or an object into two identical parts.

What are some ways to see if a shape or figure has a line of symmetry?

Draw

Draw all lines of symmetry.

Draw

Draw all lines of symmetry.

Draw

Draw all lines of symmetry.

Lines of Symmetry Continued

Remember that we can use our knowledge of lines of symmetry to find the lengths of polygons!

As long as you are able to locate a line of symmetry, you can use the line as a mirror to fill in the missing sides.

Fill in the Blanks