- The document discusses classifying triangles and quadrilaterals based on their side lengths and angles. It defines different types of quadrilaterals such as parallelograms, rectangles, rhombuses, trapezoids, and squares. - Examples are provided for classifying quadrilaterals and finding unknown angle measures using the fact that the sum of interior angles in any quadrilateral is always 360 degrees. - Students are assigned homework problems involving classifying triangles and quadrilaterals and finding unknown angle measures.

1. Lesson 8.3 , For use with pages 416-419 Classify the triangle by its side lengths. 1. 2.

2. Lesson 8.3 , For use with pages 416-419 Classify the triangle by its side lengths. ANSWER isosceles 1. ANSWER equilateral 2.

3. Quadrilaterals Section 8-3 P. 416-419

4. Essential Questions Why is it important to be able to identify congruent triangles in everyday life? Where in real life can you use the properties of isosceles and equilateral triangles? How are the relationships between lines and planes used in the real world? What areas in the real world are properties of parallel lines important?

5. Quadrilaterals Quadrilaterals are named for the number of sides. Quad means four, so a quadrilateral is 4-sided figures. Some quadrilaterals are very perfect – like a square, and others are very generic.

6. Quadrilateral = a closed figure made with four sides that are line segments. The sum of the four angles in any quadrilateral equals 360 degrees. Trapezoid = a quad. with exactly ONE PAIR of parallel sides. Parallelogram = two pairs of parallel sides Rhombus = parallelogram with 4  sides Rectangle = quad. with 4 right angles Square = a rectangle with 4  sides

7. Quadrilaterals Parallelograms Rectangle Square Rhombus Trapezoid

8. Diagonal A diagonal of a polygon connects two vertices that do not share a side. Trapezoid ABCD, name the diagonals A B C D Diagonal AC

9. The quadrilateral is a parallelogram with 4 sides of equal length. So, it is a rhombus. EXAMPLE 1 Classifying a Quadrilateral Classify the quadrilateral. The quadrilateral is a parallelogram with 4 sides of equal length and 4 right angles. So, it is a square. a. b.

10. Quadrilaterals As with triangles, all quadrilaterals have a common characteristic. The sum of the 4 angles in a quadrilateral always equals exactly 360 degrees. 90 x 4 = 360 2 @ 45 = 90 2 @ 135 = 270 Total sum of 360

11. EXAMPLE 2 Finding an Unknown Angle Measure SOLUTION The sum of the angle measures is 360 . Add. Subtract 309 from each side. Find the value of x . x + 51 + 129 + 129 = 360 x + 309 = 360 = x 51

12. GUIDED PRACTICE for Examples 1 and 2 ANSWER x = 65 Use the figure at the right. 1. Classify the quadrilateral. ANSWER The quadrilateral is a trapezoid with exactly 1 pair of parallel sides. 2. Find the value of x .

13. Classzone.com Go to the 8 th grade math book Animations Click on the left side on Chapters 7-9 Chapter 8: Drawing Quadrilaterals Chapter 8: Playing Golf with Angles

14. Homework Assignment: p. 417 – 418 #1-14, 19-24 When classifying, be as specific as possible and you only need to use one name. #6-8 You do NOT need to measure the quadrilaterals.