Mathematics Class 7
Geometric Twins
Tell whether figures match, which measurements settle a triangle, and use twins in proofs.
16 lessons · ~103 min total
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Lessons in this topic
- 0 Start here Tell when figures are exact copies, which measurements settle a triangle, and use twins. · 4 min You are here
- 1 Landing one on the other Two figures are congruent when one lands exactly on the other. · 6 min
- 2 Slide it, turn it, flip it Sliding, turning or flipping a figure does not change any side or corner. · 6 min
- 3 A bigger copy is a different figure A bigger copy keeps every corner, but its sides are longer, so it is not congruent. · 7 min
- 4 One line, one corner Segments match on length. Angles match on degrees. Tilt and arm length do not matter. · 6 min
- 5 Three sides settle it Three equal sides make two triangles congruent. This is the SSS test. · 7 min
- 6 Two sides and the corner between them Two sides and the angle between them fix a triangle. Two sides and another angle may not. · 7 min
- 7 Two corners and a side Two angles and a matching side fix a triangle. The third angle comes free. · 7 min
- 8 When shape is not enough Three equal angles fix the shape but not the size, so AAA does not prove congruence. · 7 min
- 9 Writing a congruence in order In ΔABC ≅ ΔXYZ, the letters match in order, and the order tells which corners match. · 6 min
- 10 RHS: a right angle, the hypotenuse, a side A right angle with the hypotenuse and one more side fixes a triangle. · 7 min
- 11 Equal sides, equal angles Equal sides have equal angles across from them. An equilateral triangle has three angles of 60°. · 7 min
- 12 Twins hiding in a figure Read the marks in a figure, then name the condition that proves two triangles congruent. · 7 min
- 13 Checkpoint: order, RHS and angles A quick graded check on writing congruence, RHS, equal angles and twins in figures. · 5 min
- 14 The big picture Twelve ideas on one screen. · 5 min
- 15 Track quiz A cheat-sheet table and twelve questions, one per idea. · 9 min
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