Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

terminal side

The ray where an angle's rotation ends up.

The terminal side of an angle is the ray the initial side lands on after the rotation; it shows where the rotation ended.