Chapter 1.6 Trigonometric Functions
The Unit Circle
Degree/Radian Conversion To convert a degree measure to radians, multiply by π radians180°
To convert a radian measure to degrees, multiply by 180°π radians
Examples Examples
1) 120°
2) -45°
3) 5π6
4) -3π2
Radian Measure The RADIAN MEASURE of the angle ACB at the center of the unit circle
equals the length of the arc that ACB cuts from the unit circle. Radius =1
Finding Arc Length Find the length of an arc on a circle of radius 3 by a central angle of measure
2π/3.
S = r θ
= 3(2π/3)
= 2π
An Angle θ In Standard Position
When an angle of measure θ is placed in standard position at the center of a circle of radius r, the six trigonometric functions of θ are defined as follows:
sin θ = y/r csc θ = r/y
Cos θ = x/r sec θ = r/x
Tan θ = y/x cot θ = x/y
(SOHCAHTOA) Sin – opp/hyp
Cos – adj/hyp
Tan – opp/adj
Csc – hyp/opp
Sec – hyp/adj
Cot – adj/opp
Graph of sin
Graph of cos
Graph of tan
Periodicity Periodic Function, Period: A function f(x) is periodic if there is a postive
number p such that f(x + p) = f(x) for every value of x. The smallest such value of p is the period of f.
Transformations of Trigonometric Graphs Y = a f ( b ( x + c ) ) + d
A = vertical stretch or shrink/reflection about x-axis
B = horizontal stretch or shrink/ reflection about y-axis
C = Horizontal shift
D = vertical shift
Finding Angles in degrees and Radians Find the measure of cos-1 (-0.5) in degrees and radians.
Put the calculator in degree mode and enter cos-1 (-0.5). You will get 120 degrees.
Using the Inverse Trigonometric Functions Sinx = 0.7
Take the sin-1 of both sides.
X = sin-1(0.7)
X = 0.775
Homework Quick Review pg 52 # 1-4
Section 1.6 Exercises pg 52 #1-10
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