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Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
Unit 14The Unit Circle
I understand how special right triangles are used to develop the unit circle.
I can find the sine and cosine of an angle using the unit circle.
I can draw the terminal side of an angle and find its reference angle.
I can identify coterminal angles and understand they have the same trig values.
• Its initial side is along the positive xaxis
• It is measured by rotating from the initial side to the terminal side in a counterclockwise direction.
Standard position of an angle
0o360o
90o
270o
180o Initial Side
Terminal Side
150o
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
Examples of angles in standard position
Positive(rotating counterclockwise is good)
Negative(rotating clockwise is bad)
Angles greater than 360o(revolve around more than once!)
So how do you know where the terminal side goes?
Coterminal AnglesAngles that share the same terminal side.
erase
ex) Draw and name the coterminal angle to the given angle.
300
3300 3900
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
Reference Anglethe positive, acute angle between the horizontal axis and the terminal side. AKA the angle it makes with the xaxis.
• Draw the terminal side of the angle.• Draw a triangle up or down to the xaxis• The reference angle is the one between the xaxis and the terminal side, with a vertex at the origin.
Finding the Reference Angle
ex) Draw and name the reference angle to the given angle.
think butterflies and bow ties
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
• The reference angle is the one between the xaxis and
the terminal side, with a vertex at the origin.
note
Making the link between the circle and trig.
Defining the Circular Function
(1, 2)
Goal: Find the reference angle if the point (1, 2) is on the edge of a circle.
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
(1, 2)
1
2
Find the reference angle if the point (1, 2) is on the edge of a circle.
SOH CAH TOA
(x,y)
x
y3
Find the coordinates of the point of a 30o angle if r = 3.
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
Find the coordinates of the point of a 40o angle if r = 1.
something cool happens when the radius is one!
The Unit Circle: The x-coordinate of any point on the unit circle is simply the cosine of the angle!
The y-coordinate is simply the sine of the angle!
To find x:
To find y:
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
Any point's coordinates can be found by doing...
You can now do Trig without a
calculator!!!!
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
The Unit Circle:circle centered at the origin with radius 1.
erase
(1,0)
(0,1)
(-1,0)
(0,-1)
(0,0)
Any point's coordinates can be found by doing...
(Cos θ, Sin θ)x y
erase
(1,0)
(0,-1)
cos 90o=sin 90o=
sin 270o =
cos 0o =sin 0o =
cos 180o=sin 1800 =
cos 360o =
cos 270o =
(0,1)
(-1,0)
Remember: x y(cos θ, sin θ)
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019
Positive/Negative??Where are Cosine and Sine
I
II
III IV
(Cos, Sin)
(___, ___)
(___, ___)
(___, ___)
(___, ___)
Today we have an activity to help you understand the unit circle a little better. You will need:• A paper plate for each person• 2 black markers• 2 of each high lighter (blue, pink, and yellow) • 34 protractors
You will need to share materials!
Unit 14 Unit circle Paper plates and the Unit Circle.notebook April 24, 2019Step 1: Fold your paper plate in half and then in half again making the four quadrants.
Step 2: Trace the folds and label them as the xaxis and yaxis.
Step 3: Label the origin (0,0), the points (1, 0), (0, 1), (1, 0) and (0, 1) and the degree measures 90, 180, 270, and 360.