Answer the following
problems dealing with
Coordinate Geometry proofs.
(Please Note: Answers will show only ONE
possible solution to a problem.
Even when a specific method of solution is requested, answers may vary in
presentation.)
Before you
begin, refresh your memory ...


When developing a coordinate
geometry proof:

1. draw and label the graph 
2. state the formulas you
will be using 
3. show ALL work (if
you are using your graphing calculator, be sure to show your screen displays
as part of your work.) 
4. have a concluding
sentence stating
what you have proven and why it is true. 



1. 
Prove that quadrilateral A(1,2),
B(2,5), C(5,7) and D(4,4) is a
parallelogram by using slopes. 

Proof


2. 

Prove that A(1,1),
B(4,4), C(6,2) are the vertices of a
right triangle. 
Proof


3. 
Prove that quadrilateral A(1,2),
B(13,4),
C(6,8) and D(2,4) is a
trapezoid, but is NOT an isosceles trapezoid. 

Proof


4. 

Prove that A(2,2),
B(1,4), C(2,8) and D(1,6) is a
parallelogram using midpoints. 
Proof


5. 
Prove that A(3,2),
B(2,6), C(2,7)
and D(1,3) is a
rhombus. 

Proof


6. 

Prove that A(4,1),
B(5,6), C(1,3) is an isosceles right
triangle. 
Proof


7. 
Guinevere and Lancelot see a drawing
of quadrilateral ABCD, A(2,2),
B(5,2),
C(9,1) and D(6,5).
Guinevere says the figure is a rhombus, but not a
square. Lancelot says the figure is a square.
Write a proof to show who is making the correct
observation. 

Proof


