MATH 13100 Lecture Notes - Lecture 5: Hypotenuse, Unit Circle, Even And Odd Functions
MATH 131 Lecture Notes
Trigonometric Functions (0.7)
I. Review the right triangle and its sin, cos, and tan ratios below
The ratios are: inX ,cosX ,tanXs =opposite
hypotenuse = adjacent
hypotenuse = opposite
adjacent
II. We can also define trigonometric functions using the unit circle.
A. Sine is an odd function and cosine is an even function
III. Some general identities about sine and cosine
A. and in(− ) − in(t)s t =s os(− ) os(t)c t =c
1. Sine must flip, but cos stays the same. This is because changing the sign
will change the function vertically, and not necessarily horizontally.
B. and in( ) os(t)s2
π−t=c os( ) in(t)c2
π−t=s
C. in t os ts 2+c2= 1