Exploring the Sequence of Transformations for Mapping y = sinx to y = 3sin2x

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In summary: The transformations are a stretch by a factor of 3 vertically and a "squeeze" by a factor of 1/2 horizontally. The "enlargement" is uniform along the axes.
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Describe fully the sequence of two transformations that maps the graph y = sinx onto the graph of y = 3sin2x

Well I know that when x = 45 y = 3, when x = 90 y = 0 when x = 135 y = -3 and so on, but tranformations and translation (move), reflection, rotation and englargment. I would presume that the graph is enlarged and then relected, however what is the point of enlargment?

Am I right so far?

Thanks
:biggrin:
 
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  • #2
thomas49th said:
Describe fully the sequence of two transformations that maps the graph y = sinx onto the graph of y = 3sin2x

Well I know that when x = 45 y = 3, when x = 90 y = 0 when x = 135 y = -3 and so on,
Actually, you don't know that- or shouldn't. When sine and cosine are used as functions, rather than to solve functions, the basic definitions require that arguments be interpreted as in radians. (Strictly speaking a mathematician wouldn't think of the argument as an angle at all, but calculators are designed by engineers who do!) What you should know is that when [itex]x= \pi/4[/itex], y= 3, when [itex]x= \pi/2[/itex], y= 0, etc.

but tranformations and translation (move), reflection, rotation and englargment. I would presume that the graph is enlarged and then relected, however what is the point of enlargment?

Am I right so far?

Thanks
:biggrin:
I'm not sure what you mean by "point of enlargement"- the "enlargement" is uniform along the axes. Your "base function" is sin(x). I prefer to think that anything done after the base function is a change in y, anything done before is a change is x. Here,you multiply x by 2 before taking the sine, then multiply by 3. Okay, multiplying y by 3 stretches (enlarges) the y value (height of the graph) by 3. Multiplying x by 2 before taking sine changes the graph horizontally. Normally, a sine graph goes from 0 to 0 as x changes from 0 to [itex]\pi[/itex]. Here, that happens as 2x changes from 0 to [itex]\pi[/itex]- in other words as x changes from 0 to [/itex]\pi/2[/itex]. Horizontally, the graph is "shrunk" by 1/2. There is no reflection- that would involve multiplying by -1.
 
  • #3
img020.jpg

part B. How would you answer that? At GCSE, we've never used sin with pi
 
  • #4
Yeah, I see that. I don't like but I will try to live with it!

But I told you the transformations are a stretch by a factor of 3 vertically and a "squeeze" by a factor of 1/2 horizontally.
 
  • #5
But I told you the transformations are a stretch by a factor of 3 vertically and a "squeeze" by a factor of 1/2 horizontally.

Will that get me the marks in the exam? (it's GCSE)

Thanks
 
  • #6
Technically, since it's a sine function you'd need to put that it has an amplitude of 3 instead of 1, and it's period is changed from [tex]2\pi[/tex] (or 360 degrees) to [itex]\pi[/itex] (or 180 degrees).

This is for part "b" I mean.
 
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  • #7
Feldoh said:
Technically, since it's a sine function you'd need to put that it has an amplitude of 3 instead of 1, and it's period is changed from [tex]2\pi[/tex] (or 360 degrees) to [itex]\pi[/itex] (or 180 degrees).

This is for part "b" I mean.

Those statements are true about the graph, but they are not "transformations" and the problem specifically said "describe the sequence of transformations".

As to whether "Will that get me the marks in the exam?" I have no idea! That is how I would answer the question as asked.
 
  • #8
Found an interesting document here

http://www.wilsonsschool.sutton.sch.uk/dept/mathematics/stsup/files/page90_6.doc [Broken]

and here:

http://www.bbc.co.uk/schools/gcsebitesize/maths/shapeh/anglesover90rev3.shtml [Broken]

"stretch" is a correct word
 
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1) What is the purpose of the "sin x transformation" in scientific research?

The "sin x transformation" is used to transform a non-linear relationship between two variables into a linear relationship. This allows for easier analysis and interpretation of the data.

2) How is the "sin x transformation" mathematically defined?

The "sin x transformation" is defined as taking the sine of each data point in a given dataset and using the resulting values in statistical analysis or modeling.

3) What types of data are suitable for the "sin x transformation"?

The "sin x transformation" is typically used for data that follows a curved or non-linear pattern, such as growth or decay data.

4) Are there any limitations or drawbacks to using the "sin x transformation"?

While the "sin x transformation" can be useful in certain cases, it may not always be the most appropriate or accurate way to analyze data. It is important to consider the underlying assumptions and limitations of this transformation before applying it to a dataset.

5) How does the "sin x transformation" compare to other data transformations, such as log or square root transformations?

The "sin x transformation" is one of many mathematical transformations that can be used to manipulate data. Each transformation has its own strengths and limitations, and the best one to use will depend on the specific dataset and research question at hand.

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