# Sine is a height. Let’s see why.

Join Zon for a ride around the unit circle. Connect an angle to a vertical position—and discover why sin 90° and sin 270° tell such different stories.

In this lesson, height means signed vertical position relative to the wheel’s centre. On the unit circle, the radius is 1. Make a prediction, watch the story, explore the interactive, and try questions with hints.

Canonical page: https://21ifm.com/basics/sine

## Explore

- [Next: connect sine to a launch-angle question](https://21ifm.com/basics/best-launch-angle)
- [More Basics Mathematics](https://21ifm.com/basics)
- [Watch the sine explainer video](https://21ifm.com/lessons/sine/Zon-Sine-Fixed.mp4)