Why SSA is not a criterion
- Killing a claim — 3 tasks
- Where the choice is — 3 tasks
- Two triangles from the same three parts — 3 tasks
- When the arc misses, touches or crosses — 3 tasks
- Going Deeper — 6 tasks
- Practice — 25 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.
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Why SSA Is Not a Criterion — Cut & Glue Sort 25 minutes · 5 sheets
12 drawings of an angle, a side and an arc swung from its end. Count where the arc meets the other side: two triangles, one, or none. The sort shows why SSA does not prove congruence.
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Why SSA Is Not a Criterion — Maze 10–15 minutes · 4 sheets
Eight boxes: an angle, a side, and one more length. How many triangles fit: two, one or none? Each wrong answer is a classic SSA mistake and leads to a box that sends the student back.
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Why SSA Is Not a Criterion — Mystery Picture 25–35 minutes · 4 sheets
25 squares, each two triangles and three facts in words. Do the facts prove the triangles congruent (SSS, SAS, ASA, AAS) or not (SSA, AAA)? Fill or leave white, and a picture appears.