Mathematics Class 10
Triangles
Decide if two triangles are similar, and prove the parallel-line ratio theorem.
14 lessons · ~109 min total
Track progress — 0 of 14 lessons read 0%
Lessons in this topic
- 0 Start here The road map: what similar means, three tests for similar triangles, and the parallel-line theorem. · 4 min You are here
- 1 Similar, said precisely Similar figures have equal angles and sides in one ratio. Size can differ, shape cannot. · 8 min
- 2 Two angles are enough Two matching angles make triangles similar. The third angle is forced. · 8 min
- 3 Sides in the same ratio Three side ratios that match make two triangles similar. Pair longest with longest. · 9 min
- 4 Two sides and the angle between Two side ratios and the angle between them make triangles similar. · 8 min
- 5 Heights without ladders A pole and its shadow give the sun’s ratio. Use it on a tall object’s shadow. · 9 min
- 6 Checkpoint: shapes, factors and shadows Five quick checks on similar figures, AA, SSS, SAS and shadows. · 6 min
- 7 A line parallel to one side A parallel to one side cuts the other two in one ratio. Here is the proof. · 10 min
- 8 Reading the split backwards Equal splits on two sides make the line parallel to the third. · 8 min
- 9 Checkpoint: the parallel-line pair Five quick checks on the parallel-line theorem, its proof and its converse. · 6 min
- 10 From a parallel to a similarity A parallel to BC cuts off a small triangle. It is similar to the whole. · 9 min
- 11 Which test decides it Match the corners first. Then the measurements name the test: AA, SSS, SAS, or none. · 9 min
- 12 The big picture The whole chapter on one screen: similar, AA, SSS, SAS, shadows and the parallel-line theorem. · 6 min
- 13 Track quiz A cheat-sheet table and nine quick questions on Chapter 6. · 9 min
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