# Today we will understand parallelograms ```Unit 8 Day 2 Video Notes
Parallelograms
Today we will understand parallelograms
And at the end of today, you will be able to determine lengths of diagonals, angles and sides
in a parallelogram
parallelogram –
If a quadrilateral is a parallelogram, then:
- its opposite sides are congruent.
- its opposite angles are congruent.
- its consecutive angles are supplementary.
- its diagonals bisect each other.
Examples:
1. Find the values of x and y.
x+ 4
y
65
12
2. Find the indicated measure given the JKLM is a parallelogram.
a. NM
b. KM
c. m  JML
d. m  KML
K
L
2
N
110
30
J
3. Find the values of a and b in the parallelogram.
M
a - 12
(b + 10)
36
30
4. Find the indicated measures in parallelogram ABCD.
B
C
a. m  BCD
100
b. If BE = 9, find BD.
E
37
A
D
How do I know if a quadrilateral is a parallelogram?
If….
- both pairs of opposite sides of a quadrilateral are congruent
- both pairs of opposite angles of a quadrilateral are congruent
- one pair of opposite sides of a quadrilateral are congruent and parallel
- the diagonals of a quadrilateral bisect each other
Examples:
1. In quadrilateral WXYZ, m  W = 42&deg;, m  X = 138&deg;, m  Y = 42&deg;. Find m  Z. Is WXYZ a
parallelogram?
C
2. For what value of x is quadrilateral CDEF a parallelogram?
5x - 8
F
3x
D
E
What reasoning can you use to show that the quadrilateral is a parallelogram?
3.
4.
5.
7 in
30 m
65
5 in
115
5 in
7 in
30 m
115
65
```