Precalculus Section 7.5

Warmup Graph the function. State the Domain, Range, Asymptotes, and Period 1.f(x) = -2 tan(1/3 x) 2.f(x) = sec(2x) + 1

Warmup Answers 1.f(x) = -2 tan(1/3 x) Domain: Range: Asymptotes: Period:

Warmup Answers 1.f(x) = sec(2x) + 1 Domain: Range: Asymptotes: Period:

7.5 Lesson – Unit Circle and Properties of Trig Functions You do not need to write down the information on this slide in your notes We have actually already done most of this section: we have talked about the unit circle and we discussed domain, range, and period while graphing the trig functions Today we will be adding one property: odd- even properties

7.5 Lesson – Unit Circle and Properties of Trig Functions You do not need to attempt to copy the following graphs Look for SYMMETRY in the graphs – Could the function be reflected over a line or a point? – Example: Reflected over y-axis or reflected over origin

What is the graph of f(x) = x ?

What is the graph of f(x) = x 2 ?

What is the graph of f(x) = x 3 ?

What is the graph of f(x) = x 4 ?

What is the graph of f(x) = x 5 ?

What is the graph of f(x) = x 6 ?

Do you see the pattern? Odd powers: Even powers:

(Write this down) An “odd” function reflects over the origin An “even” function reflects over the y-axis

Function Notation Definitions of odd and even functions Odd function: f(-x) = - f(x) Even function: f(-x) = + f(x)

Graphical Example (odd)

Graphical Example (even)

Is sine odd or even? Graph the base graph of sine and determine if it is odd or even

Is sine odd or even?

Sine is odd On your green sheet of trig rules, find the odd- even properties and write: sin(- x) = - sin(x)

Is cosine odd or even? Graph the base graph of cosine and determine if it is odd or even

Is cosine odd or even?

Cosine is even On the green sheet write: cos(- x) = cos(x)

Is tangent odd or even? Graph the base graph of tangent and determine if it is odd or even

Is tangent odd or even?

Tangent is odd On your green sheet write: tan(- x) = - tan(x)

What about the other three? The other three functions (secant, cosecant, and cotangent) will have the same property as its reciprocal On your green sheet add the red part: sin(- x) = - sin(x)(and csc) cos(- x) = cos(x)(and sec) tan(- x) = - tan(x)(and cot)

Using the odd-even properties Find the exact value of sin(-45°)

Using the odd-even properties Find the exact value of cos(-120°)

Using the odd-even properties Find the exact value of

Using the odd-even properties (try this on your own) Find the exact value of

Another Example If f(x) = cos(x) and f(a) = ¼, find the exact value of f(-a) Answer: Since cosine is even, f(-a) = f(a) Since f(a) = ¼, f(-a) = ¼

Example continued If f(x) = cos(x) and f(a) = ¼, find the exact value of f(a) + f(a + 2π) Answer: Since the period of cosine is 2π, f(a + 2π) will equal f(a) (think about the graph and how cos(0) = cos(2π) ) So we have f(a) + f(a + 2π) = ¼ + ¼ = 2/4 = ½

HW Time You may use the rest of the period to work on homework