1. Over Lesson 11–3 A.A B.B C.C D.D 5-Minute Check 1 Find the measure of all angles on the drawing below if m<1=126˚

2. Splash Screen

3. Then/Now You learned about angles (Previous course and Lesson 11-1) You learned about the sum of the angles of a triangle (Previous course) Find missing angle measures of a quadrilateral. Classify quadrilaterals.

4. Vocabulary quadrilateral A closed figure with four sides and four vertices, examples are squares, rectangles, and trapezoids

5. Concept

6. Example 1 Find Angle Measures ALGEBRA Find the value of x in the quadrilateral. Then find each missing angle measure. The sum of the measures of the angles is 360°. Let m  Q, m  R, m  S, and m  T represent the measures of the angles.

7. Example 1 Find Angle Measures m  Q + m  R + m  S + m  T=360Angles of a quadrilateral 75 + 4x + 110 + x=360Substitution 5x + 185=360Combine like terms. 5x + 185 – 185=360 – 185Subtract 185 from each side. 5x=175Simplify. x=35Divide each side by 5. Answer: So, m  T = 35° and m  R = 4(35) or 140°.

8. A.A B.B C.C D.D Example 1 A.x = 4; m  A = 4° and m  C = 16° B.x = 5; m  A = 5° and m  C = 20° C.x = 40; m  A = 40° and m  C = 160° D.x = 104; m  A = 104° and m  C = 416° Find the value of x. Then find each missing angle measure.

9. Quadrilaterals Trapezoids Parallelograms Other Quadrilaterals Rhombus Rectangles Squares

10. Example 2 Classify Quadrilaterals Answer: parallelogram Classify the quadrilateral shown using the name that best describes it. The quadrilateral has both pairs of opposite sides parallel and congruent.

11. A.A B.B C.C D.D Example 2 A.square B.rectangle C.rhombus and rectangle D.parallelogram and square QUILT PATTERN The figure shows a pattern for the border of a quilt. Classify the quadrilaterals used to form the flower and the leaves using the name that best describes them.

12. End of the Lesson