Select the correct answer:

Triangle ABC is reflected across the [tex]$y$[/tex]-axis and then dilated by a factor of [tex]$\frac{1}{2}$[/tex] centered at the origin. Which statement correctly describes the resulting image, triangle DEF?

A. The reflection preserves the side lengths and angles of triangle ABC. The dilation preserves angles but not side lengths.
B. Both the reflection and dilation preserve the side lengths and angles of triangle ABC.
C. Neither the reflection nor the dilation preserves the side lengths and angles of triangle ABC.
D. The dilation preserves the side lengths and angles of triangle ABC. The reflection does not preserve side lengths and angles.



Answer :

When we transform a shape through reflection and dilation, it's important to understand how these transformations affect various properties of the shape such as side lengths and angles.

First, consider the reflection across the [tex]\( y \)[/tex]-axis:

1. Reflection Across the [tex]\( y \)[/tex]-Axis:
- When a triangle is reflected across the [tex]\( y \)[/tex]-axis, its image will be a mirror image.
- The reflection preserves both the side lengths and angles of the original triangle. This is because the reflection is an isometry, meaning the distances and angles are maintained.
- Therefore, after reflecting Triangle ABC across the [tex]\( y \)[/tex]-axis, the resulting triangle still has the same side lengths and angles as Triangle ABC.

Next, consider the dilation centered at the origin by a factor of [tex]\(\frac{1}{2}\)[/tex]:

2. Dilation by a Factor of [tex]\(\frac{1}{2}\)[/tex] Centered at the Origin:
- Dilation is a transformation that changes the size of a figure but not its shape.
- Specifically, a dilation by a factor of [tex]\(\frac{1}{2}\)[/tex] will reduce the side lengths of the triangle to half of their original lengths.
- This dilation maintains the same angles because all linear dimensions are scaled by the same factor. Thus, the proportional relationships between the side lengths remain, and the angles stay unchanged.
- Therefore, after the dilation, Triangle DEF will have side lengths that are half of those of the reflected triangle, but the angles will remain the same.

Putting these two transformations together:

- The reflection across the [tex]\( y \)[/tex]-axis preserves the side lengths and angles of Triangle ABC.
- The dilation by a factor of [tex]\(\frac{1}{2}\)[/tex] preserves the angles but scales the side lengths by [tex]\(\frac{1}{2}\)[/tex].

Therefore, the correct statement describing the resulting image, triangle DEF, would be:

A. The reflection preserves the side lengths and angles of triangle ABC. The dilation preserves angles but not side lengths.