Lesson 2.7Math~55 min

Angles, circles & waves

Sine and cosine from a point walking round a circle — used for rotations, similarity and transformer positions.

Module 2 · 0/9 done

Turning, measured

Trigonometry sounds scary, but it’s about one simple thing: turning. Take a circle of radius 1 (the unit circle) and walk around it. At any angle, ask two questions: how far right am I, and how far up?

Those two answers have names: cosine (how far across) and sine (how far up). That’s all $\cos$ and $\sin$ are.

Fig 2.12Drag the point around the circle (or press Spin). Cosine is its shadow on the horizontal axis, sine its shadow on the vertical one. Unroll the sine as the angle grows and you get a wave.