Writing coordinate proofs
- The page that is all true and still wrong — 3 tasks
- What a last sentence has to do — 3 tasks
- Writing the last sentence — 3 tasks
- Two claims, two sentences — 3 tasks
- Going Deeper — 6 tasks
- Practice — 21 tasks
- Summary — 2 tasks
- Cool-down — 3 tasks
Classroom activities
Things a class does rather than writes on. Each one is a finished PDF: print it, cut it up if it says so, and hand it round.
-
Does the Proof Work? Writing Coordinate Proofs — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 short coordinate proofs, each with its numbers and its last sentence. Students sort each one: correct, the last sentence names a rule the numbers do not show, or the numbers are not enough. Four lengths with a sentence about parallel sides, one pair of parallel sides called a parallelogram, and numbers for one rectangle used to prove a claim about every rectangle are all in the mix.
-
Write the Last Sentence — Writing Coordinate Proofs Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page, each a coordinate proof with its slopes, lengths or midpoints already computed. Students pick the last sentence: the one that names the rule the numbers show, and all of that rule. Each wrong sentence is a classic mistake: four lengths and a sentence about parallel sides, or a rectangle with no right angle named. The row of box numbers at the foot is the check.
-
Do the Numbers Prove It? Writing Coordinate Proofs — Mystery Picture 25–35 minutes · 4 sheets
25 squares, each one line of a coordinate proof: slopes, lengths or midpoints already computed, then "so", then a claim. Students compute nothing. They decide whether the numbers prove the claim. Fill it or leave it white, and a picture appears. The white squares are the classic mistakes: equal lengths used to prove sides parallel, four congruent sides called a square, and numbers for one rectangle used for every rectangle.