HiSET: Math : Understand transformations in the plane

Study concepts, example questions & explanations for HiSET: Math

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Example Questions

Example Question #92 : Hi Set: High School Equivalency Test: Math

What is the result of reflecting the point  over the y-axis in the coordinate plane?

Possible Answers:

Correct answer:

Explanation:

Reflecting a point

over the y-axis geometrically is the same as negating the x-coordinate of the ordered pair to obtain

.

Thus, since our initial point was

 

and we want to reflect it over the y-axis, we obtain the reflection by negating the first term of the ordered pair to get

.

Example Question #1 : Reflections

Symmetry

How many lines of symmetry does the above figure have?

Possible Answers:

One

Two

Four

None

Infinitely many

Correct answer:

One

Explanation:

A line of symmetry of a figure is about which the reflection of the figure is the figure itself. The diagram below shows the only line of symmetry of the figure.

Symmetry

The correct response is one.

Example Question #3 : Understand Transformations In The Plane

On the coordinate plane, the point  is reflected about the -axis. The image is denoted . Give the distance .

Possible Answers:

Correct answer:

Explanation:

The reflection of the point at  about the -axis is the point at ; therefore, the image of  is . Since these two points have the same -coordinate, the distance between them is the absolute value of the difference between their -coordinates:

Example Question #2 : Reflections

Consider regular Hexagon ; let and be the midpoints of and . Reflect the hexagon about , then again about . Which of the following clockwise rotations about the center would result in each point being its own image under this series of transformations?

Possible Answers:

Correct answer:

Explanation:

Refer to the figure below, which shows the reflection of the given hexagon about  ; we will call the image of , call the image of , and so forth.

 Hexagon

Now, refer to the figure below, which shows the reflection of the image about  ; we will call  the image of , call  the image of , and so forth.

 Hexagon

 

Note that the vertices coincide with those of the original hexagon, and that the images of the points are in the same clockwise order as the original points. Since coincides with , coincides with , and so forth, a clockwise rotation of five-sixth of a complete turn - that is, ,

is required to make each point its own image under the three transformations.

Example Question #1 : Reflections

Consider regular Hexagon ; let and be the midpoints of and . Reflect the hexagon about , then again about . With which of the following points does the image of under these reflections coincide?

Possible Answers:

 

Correct answer:

Explanation:

Refer to the figure below, which shows the reflection of about ; we will call this image .

Hexagon

 

Note that  coincides with . Now, refer to the figure below, which shows the reflection of  about ; we will call this image - the final image - 

 Hexagon

 

Note that  coincides with , making this the correct response.

Example Question #1 : Understand Transformations In The Plane

 

Translation

The graph on the left shows an object in the Cartesian plane. A transformation is performed on it, resulting in the graph on the right. 

Which of the following transformations best fits the graphs?

Possible Answers:

Rotation about the origin

Reflection in the y-axis

Translation

Dilation

Reflection in the x-axis

Correct answer:

Translation

Explanation:

A dilation is the stretching or shrinking of a figure.

A rotation is the turning of a a figure about a point. 

A reflection is the flipping of a figure across a line.

A translation is is the sliding of a figure in a direction. 

With a translation, the image is not only congruent to its original size and shape, but its orientation remains the same. A translation fits this figure best because the shape seems to move upward and rightward without changing size, shape, or orientation.

Example Question #2 : Translations

Translate the graph of the equation

left four units and down six units. Give the equation of the image.

Possible Answers:

Correct answer:

Explanation:

If the graph of an equation is translated to the right units, and upward  units, the equation of the image can be found by replacing  with  and  with  in the equation of the original graph. 

Since we are moving the graph of the equation

left four units and down six units, we set and ; we can replace with , or , and with , or . The equation of the image can be written as

Simplify by distributing:

Collect like terms:

Add 26 to both sides:

,

the correct choice.

Example Question #6 : Understand Transformations In The Plane

Translate the graph of the equation

right two units and up five units. Give the equation of the image.

Possible Answers:

None of the other choices gives the correct response.

Correct answer:

Explanation:

If the graph of an equation is translated to the right units, and upward  units, the equation of the image can be found by replacing  with  and  with  in the equation of the original graph. 

Since we are moving the graph of the equation

right two units and up five units, we set  and ; we can therefore replace  with and  with . The equation of the image can be written as 

This can be rewritten by applying the binomial square pattern as follows:

Collect like terms; the equation becomes

Subtract 100 from both sides:

Example Question #102 : Hi Set: High School Equivalency Test: Math

Translate the graph of the equation

right four units and down two units. Give the equation of the image.

Possible Answers:

Correct answer:

Explanation:

If the graph of an equation is translated to the right units, and upward  units, the equation of the image can be found by replacing  with  and  with  in the equation of the original graph. 

Since we are moving the graph of the equation

right four units and down two units, we set  and ; we can therefore replace  with , and  with , or . The equation of the image can be written as

The expression at right can be simplified. First, use the distributive property on the middle expression:

Now, simplify the first expression by using the binomial square pattern:

Collect like terms on the right:

Subtract 2 from both sides:

,

the equation of the image.

Example Question #103 : Hi Set: High School Equivalency Test: Math

Translate the graph of the equation

left three units and down five units. Give the equation of the image.

Possible Answers:

None of the other choices gives the correct response.

Correct answer:

Explanation:

If the graph of an equation is translated to the right units, and upward  units, the equation of the image can be found by replacing  with  and  with  in the equation of the original graph. 

Since we are moving the graph of the equation

left three units and down five units, we set and ; we can therefore replace  with , or , and  with , or . The equation of the image can be written as

We can simplify the expression on the right by distributing:

Collect like terms:

Subtract 5 from both sides:

,

the correct equation of the image.

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