TRG010 · Trigonometry · Classes 11–12
Unit circle
The unit circle (radius 1) defines sine and cosine for every angle: the point at angle θ is (cos θ, sin θ).
(cos θ, sin θ)Unit circle
📐 Formula
P(θ) = (cos θ, sin θ); x² + y² = 1
✏️ Worked example
θ = 120°: P = (−0.5, 0.866), so cos 120° = −0.5 and sin 120° ≈ 0.866.
🌍 Where it is used
Rotations in graphics, circular motion, waves.
❓ Quick check
Point at 180° on the unit circle?
🏋️ Practice
EasyPoint at 90°?
Answer: (0, 1)
Mediumsin 270° = ?
Answer: −1
Challengecos 360° = ?
Answer: 1