Classifying triangles on the coordinate plane
- Two slopes that are opposites — 3 tasks
- Two answers, both incomplete — 3 tasks
- Which two sides are the same length — 3 tasks
- One comparison, three angle names — 3 tasks
- Nine cells, three of them empty — 3 tasks
- Practice — 24 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.
-
Isosceles or Not? Classifying Triangles on the Coordinate Plane — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 pieces, each telling something about a triangle: its corners, its side lengths, some slopes, or a drawing. Students sort each one: isosceles, not isosceles, or cannot tell. Opposite slopes that do not make equal sides, a triangle that looks isosceles and is not, and lengths written in two radical forms are all in the mix.
-
Name the Triangle in Two Words — Classifying Triangles on the Coordinate Plane Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page, each giving a triangle by its three corners. Students find the squares of the sides and name the triangle in two words, such as isosceles right. Each wrong name is wrong in one word, and it comes from a classic mistake: adding the wrong two squares, or using slopes to decide that two sides are equal. The row of box numbers at the foot is the check.
-
Slopes or Lengths? Classifying Triangles on the Coordinate Plane — Mystery Picture 25–35 minutes · 4 sheets
25 squares, each making one claim about a triangle: isosceles, obtuse, a right angle at a corner, the longest side. Students compute nothing. They decide whether the slope test could settle the claim, or only the side lengths can. Fill it or leave it white, and a picture appears. The white squares are the classic mistakes: using slopes to show two sides are equal, or to tell acute from obtuse.
-
Which Side Is Longest? Classifying Triangles on the Coordinate Plane — Scavenger Hunt a full class period · 13 sheets
16 cards around the room, each giving a triangle by its three corners. Students find the square of each side, across squared plus up squared, and walk to the card showing the largest. That is the first step of telling acute, right and obtuse triangles apart. Taking the side with the biggest single step, or losing a minus sign, lands on a card that sends the group back, and a clean run is 8 lines.