Lesson 9.2 Coordinate Proofs

Lesson 9.2: Coordinate Proofs

By CHRISTOPHER CAVIN

Multiple Select

What is the trapezoid midsegment theorem? Select TWO correct answers

• If a segment connects two angles of a trapezoid, that line is half the length of the base.

• If a segment connects the midpoints of the two legs of a trapezoid, it is parallel to the bases

• If a segment connects the midpoints of the bases of a trapezoid, it will divide the trapezoid into two congruent triangles.

• If a segment connects the midpoints of the two legs of a trapezoid, its length is the average of the bases.

​We use variables to show it works in ALL cases
We will work on proof on next slide
Keep in mind the following:
1) the midpoint formula
2) the slope formula
3) Even though we are working with variables,
they will act just like normal numbers.

​Plan a proof to show that the diagonals of a square are congruent and perpendicular.

​Review questions from previous topics

Multiple Choice

An interior designer wants the center of a circular fountain to be equidistant from the sides of a triangular lobby. Where should he place the center of the fountain?

• circumcenter

• incenter

• centroid

• orthocenter

Multiple Choice

Solve for x.

• 20.35
• 12.72
• 14.99
• 21.83

Multiple Choice

Solve for x.

• 38.66
• 36.87
• 53.13
• 45.71

Multiple Choice

The figure is a parallelogram.  
Solve for x.  

• 7
• 2
• 0
• 4

Multiple Choice

To prove that the following parallelogram PQRS is a rhombus, which of the following must not be true?

• PQ≅PS

• PR⊥SQ

• ∠7≅∠10 and ∠6≅∠9

• ∠8≅∠1 and ∠4≅∠5