Sumy is working in geometry class and is given figure ABCD in the coordinate plane to reflect. The coordinates of point [tex]\( D \)[/tex] are [tex]\( (a, b) \)[/tex] and she reflects the figure over the line [tex]\( y = x \)[/tex]. What are the coordinates of the image [tex]\( D' \)[/tex]?

A. [tex]\( (a, -b) \)[/tex]
B. [tex]\( (b, a) \)[/tex]
C. [tex]\( (-a, b) \)[/tex]
D. [tex]\( (-b, -a) \)[/tex]



Answer :

Reflecting a point over the line [tex]\( y = x \)[/tex] involves swapping the [tex]\( x \)[/tex] and [tex]\( y \)[/tex] coordinates of the point. Let's go through this step-by-step:

1. Understand the reflection over [tex]\( y = x \)[/tex]:
- When reflecting a point [tex]\((x, y)\)[/tex] over the line [tex]\( y = x \)[/tex], the new point becomes [tex]\((y, x)\)[/tex]. This means the [tex]\( x \)[/tex]-coordinate becomes the [tex]\( y \)[/tex]-coordinate and the [tex]\( y \)[/tex]-coordinate becomes the [tex]\( x \)[/tex]-coordinate.

2. Given point [tex]\( D \)[/tex]:
- The coordinates of point [tex]\( D \)[/tex] are [tex]\((a, b)\)[/tex].

3. Swap the coordinates:
- To reflect [tex]\( D \)[/tex] over the line [tex]\( y = x \)[/tex], we swap the [tex]\( x \)[/tex] (which is [tex]\( a \)[/tex]) and [tex]\( y \)[/tex] (which is [tex]\( b \)[/tex]) coordinates. Thus, the coordinates of the reflected point [tex]\( D' \)[/tex] are [tex]\((b, a)\)[/tex].

Therefore, the coordinates of the image [tex]\( D' \)[/tex] after reflecting [tex]\( D \)[/tex] over the line [tex]\( y = x \)[/tex] are [tex]\((b, a)\)[/tex].

So, the correct answer is:

[tex]\( \boxed{(b, a)} \)[/tex]