The general form of the sine function and the various transformations that may be done to it: amplitude, period, phase shift, vertical shit and reflections.
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Applied Math 40S Slides May 17, 2007
1. Let's look at the weather ...
Winnipeg Weather Data as of May 15, 2007 for the last year
Temperature
Month J F MAM J J A SO N D
Mean -17 -14 -6 4 12 17 20 18 12 6 -4 -14
Source: Winnipeg weather statistics
2.
3. Hours of Sunshine
Month J F MAM J J A SON D
Mean 120 140 178 232 277 291 322 286 189 150 95 99
Source: Winnipeg weather statistics
swivel your data
5. In general form, the equation and graph of the basic sine function is:
ƒ(x) = AsinB(x - C) + D
A=1, B=1, C=0, D=0
2π
-2π
-π π
Note that your calculator displays:
ƒ(x) = asin(bx - c) + d
The quot;starting point.quot;
Which is equivalent to:
ƒ(x) = AsinB(x - c/b) + D
In general form, the equation and graph of the basic cosine function is:
ƒ(x) = AcosB(x - C) + D The quot;starting point.quot;
-2π 2π
Since these graphs are so similar
(they differ only by a quot;phase -π π
shiftquot; of π/2 units) we will limit A=1, B=1, C=0, D=0
our study to the sine function.
6. The Role of Parameter A
The amplitude is the absolute value of A; |A|. It is the distance from the
sinusoidal axis to a maximum (or minimum). If it is negative, the graph
is reflected (flips) over the sinusoidal axis.
7. The Role of Parameter B
B is not the period; it determines the period according to this relation:
or
8. The Role of Parameter C
C is called the phase shift, or horizontal shift, of the graph.
9. The Role of Parameter D
D is the sinusoidal axis, average value of the function, or the vertical shift.
D > 0 the graph shifts up D units.
D < 0 the graph shifts down D units.