Trigonometry A — Triangles & the Unit Circle
Part 1 of 2. Right-triangle ratios (SOH-CAH-TOA), the Pythagorean theorem, and the unit circle that extends sine & cosine to every angle.
Trigonometry started as the study of triangles, but its real superpower is describing anything that repeats — waves, rotations, tides, AC current. This is part 1 of 2; everything is live, so change a number and the diagrams redraw to scale.
- 01 Right triangles — SOH-CAH-TOA ELI5: in a right triangle, each acute angle is fixed by the ratio of two sides — not their size. Shrink the triangle and the ratios (hence the angle) stay put.…
- 02 The unit circle ELI5: triangles only handle angles up to 90°. To go all the way around, trig moves to the unit circle — a circle of radius 1 where a point at angle φ has…
next course: Trigonometry B — Waves & the Triangle Laws →