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posted by  mgmaster on 10/6/2008 12:52:19 AM  |  status: Live  

Sinusoids

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I need to graph three periods of the function y=20sin4x. Thanks.

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posted by sneal27 on 10/6/2008 1:11:46 AM  |  status: Live
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Well if you have a trig function the general rule of thumb for graphing is:
Asin(nx)

A=Amplitude, which is the maximum y value you graph.
Period= 2π/n

So for graphing three periods of y=20sin4x you'll need to map the sin function from a range of 0 to 3 x (2π/4) = 3π/2. You're y values will be 20 to -20.



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posted by EMFN on 10/6/2008 1:59:50 AM  |  status: Live
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Honestly, you can just make an (x, y) table, select different points for x to find y values and then graph your points on the xy-plane.
 
To use trig, the first thing to do is find out how much 4x varies between 0 and 2π.
 
Why 2π?  Basically because the sine function is periodic with 2π.  This means the sine function
repeats itself on the xy-plane every 2π units to the left and right of the origin without end.
 
 
Dividing each term by 4 we get the following:
 
 
There has been no phase shift.  Look at the zeros on the left side of each inequality and you will see that we went from 0 to 0 = no phase shift.
 
The period is:
 
In this sample, the given function is periodic with π/2. 
 
Let x = the following values:
 
 
I gave you more than 3 values.
 
Select the x values you like and simplify using a calculator to find the y values.
 
Afterward, graph your three points in the (x, y) form on the xy-plane.
 
 
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