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

2. EXAMPLE 2 Finding an Unknown Angle Measure Find the value of x. SOLUTION The sum of the angle measures is 360. x + 51 + 129 + 129 = 360 x + 309 = 360 Add. = x51 Subtract 309 from each side.

3. GUIDED PRACTICE for Examples 1 and 2 Use the figure at the right. 1. Classify the quadrilateral. ANSWER The quadrilateral is a trapezoid with exactly 1 pair of parallel sides.

4. GUIDED PRACTICE for Examples 1 and 2 2. Find the value of x. Use the figure at the right. ANSWER x = 65