GEOMETRY COORDINATE GEOMETRY Proofs
Name ______
Period ______Table of Contents
Day 1: SWBAT: Use Coordinate Geometry to Prove Right Triangles and Parallelograms Pgs: 2 – 8 HW: Pgs: 9 – 12
Day 2: SWBAT: Use Coordinate Geometry to Prove Rectangles, Rhombi, and Squares Pgs: 13 - 18 HW: Pgs: 19 – 21
Day 3: SWBAT: Use Coordinate Geometry to Prove Trapezoids Pgs: 22 - 26 HW: Pgs: 27 – 28
Day 4: SWBAT: Practice Writing Coordinate Geometry Proofs (REVIEW) Pgs: 29 - 31
Day 5: TEST
Coordinate Geometry Proofs
Slope: We use slope to show parallel lines and perpendicular lines.
Parallel Lines have the same slope
Perpendicular Lines have slopes that are negative reciprocals of each other.
Midpoint: We use midpoint to show that lines bisect each other.
Lines With the same midpoint bisect each other
Midpoint Formula:
xx1 2 yy12 mid , 22
Distance: We use distance to show line segments are equal.
You can use the Pythagorean Theorem or the formula:
2 2 d (x) (y)
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Day 1 – Using Coordinate Geometry To Prove Right Triangles and Parallelograms
Warm – Up
Explaination:______
Explaination:______
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Proving a triangle is a right triangle
Method: Calculate the distances of all three sides and then test the Pythagorean’s theorem to show the three lengths make the Pythagorean’s theorem true.
“How to Prove Right Triangles”
1. Prove that A (0, 1), B (3, 4), C (5, 2) is a right triangle.
Show:
Formula:
d (x)2 (y)2
Work: Calculate the Distances of all three sides to show Pythagorean’s Theorem is true.
a2 + b2 = c2
( )2 + ( )2 = ( )2
Statement:
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“How to Prove an Isosceles Right Triangles”
Method: Calculate the distances of all three sides first, next show two of the three sides are congruent, and then test the Pythagorean’s theorem to show the three lengths make the Pythagorean’s theorem true.
2. Prove that A (-2, -2), B (5, -1), C (1, 2) is a an isosceles right triangle.
Show:
Formula:
2 2 d (x) (y)
Work: Calculate the Distances of all three sides to show Pythagorean’s Theorem is true.
_____ _____
a2 + b2 = c2
( )2 + ( )2 = ( )2
Statement:
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Proving a Quadrilateral is a Parallelogram
Method: Show both pairs of opposite sides are equal by calculating the distances of all four sides.
Examples 3. Prove that the quadrilateral with the coordinates L(-2,3), M(4,3), N(2,-2) and O(-4,-2) is a parallelogram.
Show:
Formula:
d (x)2 (y)2
Work: Calculate the Distances of all four sides to show that the opposite sides are equal.
_____ _____ AND _____ _____
Statement:
______is a parallelogram because ______.
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PRACTICE SECTION:
Example 1: Prove that the polygon with coordinates A(1, 1), B(4, 5), and C(4, 1) is a right triangle.
Example 2: Prove that the polygon with coordinates A(4, -1), B(5, 6), and C(1, 3) is an isosceles right triangle.
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Example 3: Prove that the quadrilateral with the coordinates P(1,1), Q(2,4), R(5,6) and S(4,3) is a parallelogram.
Challenge
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SUMMARY
Proving Right Triangles
Proving Parallelograms
Exit Ticket
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Homework
1.
2.
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3.
4.
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6. Prove that quadrilateral LEAP with the vertices L(-3,1), E(2,6), A(9,5) and P(4,0) is a parallelogram.
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7.
8.
9.
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Day 2 – Using Coordinate Geometry to Prove Rectangles, Rhombi, and Squares
Warm – Up
1.
2.
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Proving a Quadrilateral is a Rectangle
Method: First, prove the quadrilateral is a parallelogram, then that the diagonals are congruent.
Examples: 1. Prove a quadrilateral with vertices G(1,1), H(5,3), I(4,5) and J(0,3) is a rectangle.
Show:
Formula: d (x)2 (y)2
Work Step 1: Calculate the Distances of all four sides to show that the opposite sides are equal.
_____ _____ AND _____ _____
______is a parallelogram because ______.
Step 2: Calculate the Distances of both diagonals to show they are equal.
_____ _____
Statement:
______is a rectangle because ______.
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Proving a Quadrilateral is a Rhombus
Method: Prove that all four sides are congruent.
Examples: 2. Prove that a quadrilateral with the vertices A(-1,3), B(3,6), C(8,6) and D(4,3) is a rhombus.
Show:
Formula: d (x)2 (y)2
Work Step 1: Calculate the Distances of all four sides to show that all four sides equal.
_____ _____ _____ _____
Statement:
______is a Rhombus because ______.
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Proving that a Quadrilateral is a Square
Method: First, prove the quadrilateral is a rhombus by showing all four sides is congruent; then prove the quadrilateral is a rectangle by showing the diagonals is congruent.
Examples: 3. Prove that the quadrilateral with vertices A(-1,0), B(3,3), C(6,-1) and D(2,-4) is a square.
Show:
Formula: d (x)2 (y)2
Work Step 1: Calculate the Distances of all four sides to show all sides are equal.
_____ _____ _____ _____
______is a ______.
Step 2: Calculate the Distances of both diagonals to show they are equal.
_____ _____
______is a ______.
Statement:
______is a Square because ______.
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SUMMARY
Proving Rectangles Proving Rhombi
Proving Squares
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Challenge
Exit Ticket
1.
2.
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DAY 2 - Homework
1. Prove that quadrilateral ABCD with the vertices A(2,1), B(1,3), C(-5,0), and D(-4,-2) is a rectangle.
2. Prove that quadrilateral PLUS with the vertices P(2,1), L(6,3), U(5,5), and S(1,3) is a rectangle.
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3. Prove that quadrilateral DAVE with the vertices D(2,1), A(6,-2), V(10,1), and E(6,4) is a rhombus.
4. Prove that quadrilateral GHIJ with the vertices G(-2,2), H(3,4), I(8,2), and J(3,0) is a rhombus.
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5. Prove that a quadrilateral with vertices J(2,-1), K(-1,-4), L(-4,-1) and M(-1, 2) is a square.
6. Prove that ABCD is a square if A(1,3), B(2,0), C(5,1) and D(4,4).
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Day 3 – Using Coordinate Geometry to Prove Trapezoids
Warm - Up
1.
2.
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Proving a Quadrilateral is a Trapezoid
Method: Show one pair of sides are parallel (same slope) and one pair of sides are not parallel (different slopes).
Example 1: Prove that KATE a trapezoid with coordinates K(0,4), A(3,6), T(6,2) and E(0,-2).
Show:
Formula:
Work Calculate the Slopes of all four sides to show 2 sides are parallel and 2 sides are nonparallel.
______and ______
Statement:
______is a Trapezoid because ______.
23
Proving a Quadrilateral is an Isosceles Trapezoid
Method: First, show one pair of sides are parallel (same slope) and one pair of sides are not parallel (different slopes). Next, show that the legs of the trapezoid are congruent.
Example 2: Prove that quadrilateral MILK with the vertices M(1,3), I(-1,1), L(-1, -2), and K(4,3) is an isosceles trapezoid.
Show:
Formula:
d (x)2 (y)2
Work Step 1: Calculate the Slopes of all four sides to show Step 2: Calculate the distance of 2 sides are parallel and 2 sides are nonparallel. both non-parallel sides (legs) to show legs congruent.
Statement:
______is an Isosceles Trapezoid because ______.
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Practice
Prove that the quadrilateral with the vertices C(-3,-5), R(5,1), U(2,3) and D(-2,0) is a trapezoid but not an isosceles trapezoid.
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Challenge
SUMMARY
Exit Ticket
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Day 3 - Homework
1.
2.
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3. .
4. Triangle TOY has coordinates T(-4, 2), O(-2, -2), and Y(2, 0). Prove TOY is an isosceles right triangle.
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Day 4 – Practice writing Coordinate Geometry Proofs
1. The vertices of ABC are A(3,-3), B(5,3) and C(1,1). Prove by coordinate geometry that ABC is an isosceles right triangle.
2. Given ABC with vertices A(-4,2), B(4,4) and C(2,-6), the midpoints of AB and BC are P and Q, respectively, and PQ is drawn. Prove by coordinate geometry:
a. PQ║ AC b. PQ = ½ AC
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3. Quadrilateral ABCD has vertices A(-6,3), B(-3,6), C(9,6) and D(-5,-8). Prove that quadrilateral ABCD is: c. a trapezoid d. not an isosceles trapezoid
4. The vertices of quadrilateral ABCD are A(-3,-1), B(6,2), C(5,5) and D(-4,2). Prove that quadrilateral ABCD is a rectangle.
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5. The vertices of quadrilateral ABCD are A(-3,1), B(1,4), C(4,0) and D(0,-3). Prove that quadrilateral ABCD is a square.
6. Quadrilateral METS has vertices M(-5, -2), E(-5,3), T(4,6) and S(7,2). Prove by coordinate geometry that quadrilateral METS is an isosceles trapezoid.
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