A trapezoid is a quadrilateral with exactly ONE pair of parallel sides.

**In a trapezoid, the midsegment is ½ the sum of the bases and is ½ the sum of the bases. 

**In an isosceles trapezoid, diagonals are congruent.

**In an isosceles trapezoid, base angles are congruent. 

EXAMPLE 1:
QRST is a quadrilateral with vertices:
Q(-3,-2) R(-2,2) S(1,4) T(6,4)
Verify that QRST is a trapezoid. 
Do this by finding lines that are parallel.
(use formula for slope)
QR= -2-2/ -3–2
QR= 4  RS= 4-2/1–2
RS=2/3  
QT= 4- -2/6- -3
QT=2/3

ST= 4-4/6-1
ST=0 So, this is a trapezoid because RS and QT are parallel. 

Now use the distance formula to find out if this is an isosceles trapezoid. 

QR=√ (-2-2)+(-3- -2)
QR=√17 
 

ST=√(4-4)+(6-1)
ST=5 

Tonights homework is page 442 problems 9-19. Good Luck!