unit 5.1

initial side

the side of an angle that is aligned with the x-axis

terminal side

the side of an angle that is not aligned with the x-axis

direction of a positive angle

counter clockwise

direction of a negative angle

clockwise

axes labeled with degrees

axes labeled with radians

reference angle

the smallest angle connecting the terminal side and the x-axis

converting degrees to radians

multiply by π/180

converting radians to degrees

multiply by 180/π

coterminal angles

angles with the same terminal side

finding coterminal angles

positive: add 360° or 2π

negative: subtract 360° or 2π

complimentary angles

angles that add to 90°

suplimentary angles

angles that add to 180°

1 degree =

60 mins or 3600 secs

180° to radians

π radians

unit circle

length of an arc (degrees)

s = x/360 ⋅ 2πr

length of an arc (radians)

s = θr

area of a sector (degrees)

s = x/360 ⋅ πr²

area of a sector (radians)

A = θr² / 2