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15 Flashcards in this deck.
Enlargement and dilation are types of transformations that alter the size of a figure while preserving its shape. In enlargement, the figure is scaled either up or down from a fixed point, known as the center of enlargement. Dilation is a specific type of enlargement where the scale factor is positive, ensuring the figure remains similar to the original.
The scale factor determines how much a figure is enlarged or reduced. It is a ratio that compares the size of the transformed figure to the original. A scale factor greater than 1 indicates enlargement, while a scale factor between 0 and 1 indicates reduction. Mathematically, the scale factor (k) is expressed as:
$$k = \frac{\text{Image Size}}{\text{Original Size}}$$For example, if a triangle with sides of length 3 cm, 4 cm, and 5 cm is enlarged with a scale factor of 2, the new sides will measure 6 cm, 8 cm, and 10 cm respectively.
The center of enlargement is the fixed point from which all points of the figure are expanded or contracted. It plays a crucial role in determining the direction and magnitude of the transformation. The location of the center affects the position of the transformed figure in the coordinate plane.
If the center of enlargement is at the origin (0,0), the transformation can be easily represented using coordinate geometry. For instance, a point (x, y) after enlargement with scale factor k becomes (kx, ky).
When performing a dilation on a coordinate plane, each point (x, y) of the original figure is transformed to (kx, ky), where k is the scale factor. If the center of dilation is not at the origin but at point (a, b), the transformation formula adjusts to:
$$ (x', y') = (a + k(x - a), b + k(y - b)) $$For example, dilating a point (2, 3) with a scale factor of 3 around the center (1,1) results in:
$$ (x', y') = (1 + 3(2 - 1), 1 + 3(3 - 1)) = (4, 7) $$Understanding enlargement and dilation is essential in various real-life contexts, including architecture, engineering, and computer graphics. Architects use these concepts to create scale models, while engineers apply them in designing mechanical components. In computer graphics, dilation enables the resizing of images without distortion, ensuring visual consistency across different media.
Dilation is intrinsically linked to the concept of similarity in geometry. Two figures are similar if one can be obtained from the other through dilation (and possibly other transformations like rotation or translation). This relationship ensures that the figures have the same shape but differ in size, maintaining proportionality across corresponding sides and angles.
The inverse of a dilation transformation involves reversing the scale factor. If a figure is enlarged by a scale factor of k, its inverse transformation would reduce it by a scale factor of 1/k. This concept is particularly useful when comparing different scaled versions of the same figure or when restoring a figure to its original size after enlargement.
In coordinate geometry, dilation can be represented algebraically. Given a figure with coordinates, applying a dilation involves multiplying each coordinate by the scale factor. This transformation maintains the geometric properties of the figure while altering its size. Graphing software often utilizes dilation to demonstrate the effects of scaling on geometric shapes.
Consider a rectangle with vertices at (1,2), (1,4), (3,4), and (3,2). Applying a dilation with a scale factor of 2 centered at the origin transforms the vertices to (2,4), (2,8), (6,8), and (6,4). The resulting rectangle is a scaled version of the original, maintaining the same shape but with doubled dimensions.
While dilation is a type of enlargement, not all enlargements are dilations. Dilation specifically refers to scaling with a positive scale factor and centered at a point. Enlargement, more broadly, can involve scaling a figure without adhering to the constraints of having a fixed center or positive scale factor. Understanding this distinction is essential for accurately applying geometric transformations.
Aspect | Enlargement | Dilation |
Definition | Scaling a figure larger or smaller from a fixed point. | A specific type of enlargement with a positive scale factor. |
Scale Factor | Can be any real number except zero. | Must be a positive real number. |
Center of Transformation | Defined by the user, can be any point. | Specifically a fixed point around which dilation occurs. |
Shape Preservation | Yes, the shape remains similar. | Yes, ensures similarity in shape and proportionality. |
Applications | Used broadly in modeling, design, and scaling objects. | Primarily in coordinate geometry and similarity transformations. |
To remember how to perform dilations, use the mnemonic "SCALE":
Did you know that the concept of dilation is not only fundamental in mathematics but also plays a crucial role in art and design? For instance, Renaissance artists used dilation to create realistic perspectives in their paintings. Additionally, dilation is essential in modern computer graphics, enabling the seamless scaling of images and models without loss of quality.
One common mistake students make is applying the scale factor to only the x-coordinate or y-coordinate, resulting in distorted figures. For example, dilating the point (2,3) with a scale factor of 2 incorrectly applied to only the x-coordinate would give (4,3) instead of the correct (4,6). Another mistake is misidentifying the center of dilation, which can lead to incorrect placement of the transformed figure.