1. Trigonometry Day 1 ( Covers Topics in 4.1) 5 Notecards
Chapter 4
Trigonometry Day 1
( Covers Topics in 4.1)
5 Notecards

2. Angles Positive Angle (counterclockwise) Terminal side
Initial side
Terminal side
Positive Angle (counterclockwise)
Negative Angle (clockwise)
90˚
For example, on the coordinate plane:
130˚
180˚
0˚ is the positive x-axis
360˚
-70˚
Angles
270˚

3. What is a Radian?
A radian is the measure of the central angle  that intercepts an arc c equal in length to the radius of the circle:
2 radians
1 radian
The radius of the circle fits around the circumference times ( 2π ).
3 radians
4 radians
6 radians
Radian
5 radians

4. Quadrants:

5. Coterminal Angles
Two angles are coterminal if they have the same initial side and terminal side
** To find coterminal angles, either add or subtract 2π or 360°.
Coterminal Angles

6. Ex1: Find a positive and a negative coterminal angle for 125°.
Ex 2: Find a positive and negative coterminal angle for
=485°
=-235 °

7. Converting between Radians and Degrees
from Degrees to Radians
Multiply by
from Radians to Degrees
Converting between Radians and Degrees

8. 3π/2 3π/4 120˚ 225˚ Ex1: Change 270° into radians
Ex 3: Change into degrees
Ex 4: Change into degrees
3π/2
3π/4
120˚
225˚

9. Arc Length
For a circle of radius r, a central angle  ( in radians) intercepts an arc of length s:
S = r 
( is in radians) S  r
Arc Length

10. Ex 1: What is the arc length of a sector if r=4 inches and =240º
(Remember- you must convert to radians first)

11. You will now do a plate activity with your teacher .
Sketching Angles
You will now do a plate activity with your teacher .

12. Sketching an angle Sketch a graph of the following angles: 273º 2.º