160 likes | 346 Views
6 – 4 Special Parallelograms. L.E.Q. How do you use properties of diagonals of rhombuses and rectangles and determine whether a parallelogram is a rhombus or a rectangle?. Theorem 6 – 9: Rhombus Diagonals Bisect Angles. Each diagonal of a rhombus bisects two angles of the rhombus.
E N D
6 – 4 Special Parallelograms L.E.Q. How do you use properties of diagonals of rhombuses and rectangles and determine whether a parallelogram is a rhombus or a rectangle?
Theorem 6 – 9: Rhombus Diagonals Bisect Angles. • Each diagonal of a rhombus bisects two angles of the rhombus.
Theorem 6 – 10: Rhombus Diagonals are Perpendicular. • The diagonals of a rhombus are perpendicular.
Example 1: Finding Angle Measures. • MNPQ is a rhombus and • Find the measure of the numbered angles.
Find the measures of the numbered angles in the rhombus below.
Theorem 6 – 11: Diagonals of a Rectangle. • The diagonals of a rectangle are congruent.
Example 2: Finding Diagonal Length. • Find the length of the diagonals of rectangle GFED if FD = 2y + 4 and GE = 6y – 5.
Find the length of the diagonals of GFED if FD = 5y - 9 and GE = y + 5.
Theorems Used to Prove Whether a Parallelogram is a Rhombus or a Rectangle.
Theorem 6 – 12: • If one diagonal of a parallelogram bisects two angles of the parallelogram, then the parallelogram is a rhombus.
Theorem 6 – 13: • If the diagonals of a parallelogram are perpendicular, then the parallelogram is a rhombus.
Theorem 6 – 14: • If the diagonals of a parallelogram are congruent, then the parallelogram is a rectangle.
Example 3: Recognizing Special Parallelograms. • Determine whether the quadrilateral can be a parallelogram. If not, write impossible. Explain. • The quadrilateral has congruent diagonals and one angle of 60 degrees. • The quadrilateral has perpendicular diagonals and four right angles.
A diagonal of a parallelogram bisects two angles of the parallelogram. Is it possible for the parallelogram to have sides of lengths 5, 6, 5, and 6? Explain.
Example 4: Real-World Connection. • Community Service Builders use properties of diagonals to “square up” rectangular shapes like building frames and playing-field boundaries. Suppose you are on the volunteer building team at the right. You are helping to lay out a rectangular patio. Explain how to use properties of diagonals to locate the four corners.
Homework: • Pgs. 315-317 #s 2 – 20 even, 48 – 50 all.