1. Day 57 AGENDA:

2. Unit #6: Graphs and Inverses of Trig Functions
Accel Precalc
Unit #6: Graphs and Inverses of Trig Functions
Lesson 9: Modeling Real World Data & Simple Harmonic Motion
EQ 1: How can you create trig models to represent real world data?

3. Modeling Data Using Trig Functions:

4. Objective: Create a model in the form
Define the variables in the model:
A =
B =
t =
h =
k =
amplitude
new period
time
phase shift
vertical shift

5. WHY?? What VIEWING WINDOW could you use?
The table below lists the normal average high temperatures for Charlotte, NC.
Month
Temp °F
January 1
51.3
July 7
90.1
February 2
55.9
August 8
88.4
March 3
64.1
September 9
82.3
April 4
72.8
October 10
72.6
May 5
79.7
November 11
62.8
June 6 86
December 12 54
Use your graphing calculator to create a scatterplot of the data.
What VIEWING WINDOW could you use?
WHY??

6. Unlike the Sinusoids, the horizontal axis of symmetry IS NOT the x-axis!!
2. a) What is the period of the function? _________
12 months
b) Find B (in  radians) . ________
3. a) What are the minimum and maximum
temperatures?
Min = _______ Max = _______
51.3
90.1
19.4
Use these values to find the amplitude. A = _______
How can you use the amplitude and the max or min to find the
horizontal axis of symmetry? k = _______
70.7

7. Why can’t we use the “zero” function on the calculator?
Place the value for k in Y1 and graph the horizontal axis of symmetry through your data set. Trace along this line to estimate the closest zero. This value represents the horizontal shift. What is an estimated value for h for this periodic function?
h = ____________
Why can’t we use the “zero” function on the calculator?

8. 5. Put your values for A, B, h, and k into the model equation
Put your values for A, B, h, and k into the model equation. Graph this with your data by placing your model equation in Y2. How well does it seem to fit?
What is a sine function we can use to model normal high temperatures in Charlotte, NC?
y = ________________________

9. Part II: Simple Harmonic Motion

10. Simple Harmonic Motion Models:
Terms:
|A| = amplitude Maximum displacement
from point of equilibrium
Equilibrium --- object is at rest; zero point
Period --- time it takes to complete one cycle

11. Ex. 1 A buoy marking a channel in the harbor bobs up and down as the waves move past. Suppose the buoy moves a total of 6 feet from its high point to its low point and returns to its high point every 10 seconds. Assuming that at t = 0 the buoy is at its high point and the middle height of the buoy’s path is d = 0, write an equation to describe its motion.

12. Ex. 1 A buoy marking a channel in the harbor bobs up and down as the waves move past. Suppose the buoy moves a total of 6 feet from its high point to its low point and returns to its high point every 10 seconds. Assuming that at t = 0 the buoy is at its high point and the middle height of the buoy’s path is d = 0, write an equation to describe its motion.

13. Ex. 2 A weight on a spring bounces a maximum of 8 inches above and below its equilibrium (zero) point. The time for one complete cycle is 2 seconds. Write an equation to describe the motion of this weight, assume the weight is at equilibrium when t = 0.

14. Ex. 2 A weight on a spring bounces a maximum of 8 inches above and below its equilibrium (zero) point. The time for one complete cycle is 2 seconds. Write an equation to describe the motion of this weight, assume the weight is at equilibrium when t = 0.

15. Ex. 3 In a particular harbor, high and low tides occur every
12 hours. Find f(t) = Acos[B(t – C)] + D where h(t) is the
water level, in feet, t hours after midnight given the
following:
a) high tide is 10 ft and low tide, which occurs at 6 am , is 2 ft

16. Ex. 3 In a particular harbor, high and low tides occur every
12 hours. Find f(t) = Acos[B(t – C)] + D where h(t) is the
water level, in feet, t hours after midnight given the
following:
a) high tide is 10 ft and low tide, which occurs at 6 am , is 2 ft

17. Ex. 3 In a particular harbor, high and low tides occur every
12 hours. Find f(t) = Acos[B(t – C)] + D where h(t) is the
water level, in feet, t hours after midnight given the
following:
b) high tide is 12 ft and low tide, which occurs at 4 am , is 6 ft

18. Ex. 3 In a particular harbor, high and low tides occur every
12 hours. Find f(t) = Acos[B(t – C)] + D where h(t) is the
water level, in feet, t hours after midnight given the
following:
b) high tide is 12 ft and low tide, which occurs at 4 am , is 6 ft

19. Ex. 3 In a particular harbor, high and low tides occur every
12 hours. Find f(t) = Acos[B(t – C)] + D where h(t) is the
water level, in feet, t hours after midnight given the
following:
c) The average water level is 5 ft and high tide is 10 ft, which
occurs at 7 pm.

20. Ex. 3 In a particular harbor, high and low tides occur every
12 hours. Find f(t) = Acos[B(t – C)] + D where h(t) is the
water level, in feet, t hours after midnight given the
following:
c) The average water level is 5 ft and high tide is 10 ft, which
occurs at 7 pm.

21. Ex. 4 You have probably noticed that as you ride a Ferris wheel, your distance from the ground varies sinusoidally with time. When the last seat is filled and the Ferris wheel starts, your seat is at the position shown in the figure at the right. Let tbe the number of seconds that have elapsed since the Ferris wheel started. You find that it takes you 3 quiddles (a new measure of time) to reach the top, 43 above the ground, and that the wheel makes a revolution once every 8 quiddles.
The diameter of the wheel is 40 ft. Your mission, should you
choose to accept it, is to
do the following:
a) Sketch a graph of this sinusoid.

22. Ex. 4 You have probably noticed that as you ride a Ferris wheel, your distance from the ground varies sinusoidally with time. When the last seat is filled and the Ferris wheel starts, your seat is at the position shown in the figure at the right. Let t be the number of seconds that have elapsed since the Ferris
wheel started. You find that it takes you 3 quiddles (a new measure of time) to reach the top, 43 above the ground, and that the wheel makes a revolution once every 8 quiddles.The diameter of the wheel is 40 ft. Your mission, should you
choose to accept it, is to do the following:
b) What is the lowest you go as the Ferris wheel turns?
Why is this number greater than 0?
Lowest height = 3 ft
Must be greater than 0 in order for Ferris wheel to turn. Can’t hit the ground.

23. Ex. 4 You have probably noticed that as you ride a Ferris wheel, your distance from the ground varies sinusoidally with time. When the last seat is filled and the Ferris wheel starts, your seat is at the position shown in the figure at the right. Let t be the number of seconds that have elapsed since the Ferris
wheel started. You find that it takes you 3 quiddles (a new measure of time) to reach the top, 43 above the ground, and that the wheel makes a revolution once every 8 quiddles. The diameter of the wheel is 40 ft. Your mission, should you
choose to accept it, is to do the following:
c) Write a function that models this sinusoid.

24. Ex. 4 You have probably noticed that as you ride a Ferris wheel, your distance from the ground varies sinusoidally with time. When the last seat is filled and the Ferris wheel starts, your seat is at the position shown in the figure at the right. Let t be the number of seconds that have elapsed since the Ferris
wheel started. You find that it takes you 3 quiddles (a new measure of time) to reach the top, 43 above the ground, and that the wheel makes a revolution once every 8 quiddles.The diameter of the wheel is 40 ft. Your mission, should you
choose to accept it, is to do the following:
d) Predict your height above ground qt 6 quiddles, 4.3 quiddles, 9 quiddles, and 0 quiddles.

25. Ex. 4 You have probably noticed that as you ride a Ferris wheel, your distance from the ground varies sinusoidally with time. When the last seat is filled and the Ferris wheel starts, your seat is at the position shown in the figure at the right. Let t be the number of seconds that have elapsed since the Ferris
wheel started. You find that it takes you 3 quiddles (a new measure of time) to reach the top, 43 above the ground, and that the wheel makes a revolution once every 8 quiddles.The diameter of the wheel is 40 ft. Your mission, should you
choose to accept it, is to do the following:
e) How far from the ground were you when the last seat was filled?

26. Assignment:
Practice Problems: Modeling Data
Worksheet: Harmonic Motion