Radian+Measure

=__Radian Measure__ =

Radian Measure divides a circle in 2π

__***Remember:**__
**π: ratio between circumference of a circle to its diameter**



in a unit circle (where r=1): angle = arc length

in a non-unit circle: arc length = radius x angle in radians a = r Ɵ

**__ Converting angles: __**
 2 π = 360° π = 180°

__Radians --> degrees __ Ɵ = 5 π/4
 * Ex. 1 **

Ɵ = 5 π /4 x 180°/ π

Ɵ = 225 °

Ɵ = 11 π/6 Ɵ = 11 π /6 x 180°/ π Ɵ = 330 °
 * Ex. 2**

__ Degrees --> Radians __ 135 ° x π/180° (reduce) = 3π/4
 * Ex. 1 **

Ex. 2 200° x π/180° (reduce) = 10π/9

Practise: Find the following
1) sin 2π/7 2) cos π/3

__Answers:__ 1) 0.78 2) 0.5

=HOMEWORK: pg. 321 #5-8=