Trig Reference Angles & Exact Values and also RADIAN.

All Students Take Calculus (ASTC)

Letter	Quadrant	What's positive
All	QI	sin, cos, tan (and their reciprocals)
Students	QII	sin and csc only
Take	QIII	tan and cot only
Calculus	QIV	cos and sec only

Reciprocal pairs

• sin ↔ csc

• cos ↔ sec

• tan ↔ cot

θ

θ just means "the angle."

QI (Quadrant ranges)

0–90°

QII (Quadrant ranges)

90–180°

QIII (Quadrant ranges

180–270°

QIV (Quadrant ranges)

270–360°

QI (Reference angle rules)

θ (the angle)

QII (Reference angle rules)

180−θ

QIII (Reference angle rules)

θ−180

QIV (Reference angle rules)

360−θ

sin 0°

0

sin 30°

1/2 (same as cos 60°)

sin 45°

√2/2 (same as cos 45°)

sin 60°

√3/2 (same as cos 30°)

sin 90°

1

cos 0°

1

cos 30°

√3/2 (same as sin 60°)

cos 45°

√2/2 (same as sin 45°)

cos 60°

1/2 (same as sin 30°)

cos 90°

0

tan 0°

0

tan 30°

√3/3

tan 45°

1

tan 60°

√3

tan 90°

undefined

360° (Radian)

2π

180° (Radian)

π

90° (Radian)

π/2

270° (Radian)

3π/2

45° (Radian)

π/4

30° (Radian)

π/6

60° (Radian)

π/3