The SAS criterion (from the postulates)
- The card that does not decide — 3 tasks
- The letter the two sides share — 3 tasks
- What the postulate says, word by word — 3 tasks
- Two segments that cross — 3 tasks
- Going Deeper — 4 tasks
- Practice — 25 tasks
- Summary — 2 tasks
- Cool-down — 6 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.
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SSS, Included-Angle SAS, or Neither? — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 pairs of marked triangles, crossing segments and written facts, sorted into SSS, included-angle SAS, and neither — where two sides and an angle are equal but the angle is not between the sides. Crossing segments appear in two rows, so the vertical angles must be checked, not assumed.
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Is It Included-Angle SAS? — Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page: name the angle between two sides, decide whether marked triangles and crossing segments give included-angle SAS, and find the missing fact. Every wrong answer uses an angle that is not between the sides, and it goes to a box that sends the student back; the row of box numbers at the foot is the check.
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Is the Angle Between the Two Sides? — Mystery Picture 15–20 minutes · 4 sheets
25 squares, each two sides and an angle: fill the square if the angle is the included angle, between the two sides. Half are drawings with heavy sides and an arc, half are side names with no drawing, where the included angle is at the letter the two names share. When every square is right, a letter appears.