How do I graph y = 2 - sin(3x - ∏/5) without a calculator?

In summary, the student is trying to graph the function y = 2 - sin(3x - ∏/5) without a calculator and is unsure how to scale the x-axis. They have correctly determined the amplitude, period, and phase shift of the function, but are unsure how to scale the rest of the x-axis. They then have a realization that they need to scale it by ∏/30, rather than ∏/15.
  • #1
theintarnets
64
0

Homework Statement


I have to graph this function without a calculator, and I'm not sure how to scale the x axis.
y = 2 - sin(3x - ∏/5)

Homework Equations


y = Asin(Bx + C)
Period = 2∏/B
Phase Shift = -C/B

The Attempt at a Solution


I know that the graph will be reflected across the x axis
Amplitude: 1

Period: 2∏/3
Period divided by four = ∏/6

Phase Shift: (∏/5)/3 = ∏/15

My professor had told us to graph with a phase shift, you add the period/4 four times like this:

∏/15 + ∏/6 = 7∏/30
7∏/30 + ∏/6 = 12∏/30 or 2∏/5
12∏/30 + ∏/6 = 17∏/30
17∏/30 + ∏/6 = 21∏/30 or 11∏/15

I'm supposed to start the graph at the phase shift, ∏/15, but I don't know how to scale the rest of the x-axis. How do I get to 7∏/30 on the numberline from ∏/15? Gosh I feel so dumb ):
 
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  • #2
Ohhhhhhhhhhhhhhhhhhhhhhhhhh, I scale it by ∏/30 don't I? Cue facepalm.
 
  • #3
No, you don't. [itex]3x- \pi/5= 3(x- \pi/15)[/itex].
 

1. What is a sine function?

A sine function is a mathematical function that represents the relationship between the angle of a right triangle and the ratio of the length of the side opposite the angle to the length of the hypotenuse.

2. How do I graph a sine function?

To graph a sine function, you will need to plot points on a coordinate plane based on the values of the function. You can use a calculator or graphing software to help you determine these points.

3. What is the period of a sine function?

The period of a sine function is the length of one complete cycle of the graph. It is equal to 2π or the distance between two consecutive peaks or troughs.

4. How do I find the amplitude of a sine function?

The amplitude of a sine function is the distance between the center line and the highest or lowest point on the graph. It can be found by taking the absolute value of the coefficient in front of the sine function.

5. Can a sine function have a negative amplitude?

Yes, a sine function can have a negative amplitude. This means that the graph will be reflected across the x-axis compared to a sine function with a positive amplitude. The negative amplitude would be represented by a negative coefficient in front of the sine function.

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