We want to show that f(-t)=-f(t) f(-t)= sin (−t) = −y = −sin t = −f(t) and thus the sine function is odd. ∎ Now you should show that cosine is an even function and tangent is an odd function is a similar manner. You should use the above figure in your proof. 1. Statement: Show that cosine is an even function. 2. Statement: Show that tangent is an odd function. 3. Derivation: Derive a formula for cos 3 theta , in terms of cos theta  and sin theta or just cos theta.

Trigonometry (11th Edition)
11th Edition
ISBN:9780134217437
Author:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Publisher:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Chapter1: Trigonometric Functions
Section: Chapter Questions
Problem 1RE: 1. Give the measures of the complement and the supplement of an angle measuring 35°.
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We want to show that f(-t)=-f(t)
f(-t)= sin (−t) = −y = −sin t = −f(t) and thus the sine function is odd.

Now you should show that cosine is an even function and tangent is an odd function is a
similar manner. You should use the above figure in your proof.
1. Statement: Show that cosine is an even function.
2. Statement: Show that tangent is an odd function.
3. Derivation: Derive a formula for cos 3 theta , in terms of cos theta  and sin theta or just cos theta. 

Recall the following definitions from algebra regarding even and odd functions:
• A function f(x) is even if f(-x) = f(x) for each x in the domain of f.
• A function f(x) is odd if f(-x) = −f(x) for each x in the domain of f.
Also note that the graph of an even function is symmetric about the y-axis and the graph
of an odd function is symmetric about the origin.
The following proof shows that sine is an odd function. Use it as a model to prove that
cosine is an even function and that tangent is an odd function.
Statement: Show that sine is an odd function.
Proof: Let f (t) = sint and consider the following figure:
y
(x,y)
t
(x,-y)
x
Transcribed Image Text:Recall the following definitions from algebra regarding even and odd functions: • A function f(x) is even if f(-x) = f(x) for each x in the domain of f. • A function f(x) is odd if f(-x) = −f(x) for each x in the domain of f. Also note that the graph of an even function is symmetric about the y-axis and the graph of an odd function is symmetric about the origin. The following proof shows that sine is an odd function. Use it as a model to prove that cosine is an even function and that tangent is an odd function. Statement: Show that sine is an odd function. Proof: Let f (t) = sint and consider the following figure: y (x,y) t (x,-y) x
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