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