The Unit Circle and Trig Functions

The Unit Circle

Radius 1, centred at origin. Point at angle $\theta$: $(\cos\theta, \sin\theta)$.

Radians

$\pi$ radians = 180°. Convert: degrees × $\frac{\pi}{180}$.

Standard Angle Values

Degrees	Radians	$\sin$	$\cos$
0°	0	0	1
30°	$\frac{\pi}{6}$	$\frac{1}{2}$	$\frac{\sqrt{3}}{2}$
45°	$\frac{\pi}{4}$	$\frac{\sqrt{2}}{2}$	$\frac{\sqrt{2}}{2}$
60°	$\frac{\pi}{3}$	$\frac{\sqrt{3}}{2}$	$\frac{1}{2}$
90°	$\frac{\pi}{2}$	1	0

ASTC (Signs by Quadrant)

Q1: All +. Q2: Sin +. Q3: Tan +. Q4: Cos +.