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

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



Answer :

To find the coordinates of the image of point \(D\) after it has been reflected over the line \(y = x\), we need to understand the geometric transformation that occurs during this reflection.

1. Understanding Reflection Over \(y = x\):

When a point \((x, y)\) is reflected over the line \(y = x\), it gets mapped to a new point where the \(x\) and \(y\) coordinates are swapped. In essence, the coordinates \((x, y)\) become \((y, x)\).

2. Applying This Transformation:

Given the point \(D\) with coordinates \((a, b)\):
- The \(x\)-coordinate \(a\) will become the \(y\)-coordinate of the reflected point.
- The \(y\)-coordinate \(b\) will become the \(x\)-coordinate of the reflected point.

Therefore, when we reflect \((a, b)\) over the line \(y = x\), the new coordinates of the point \(D^{\prime}\) will be \((b, a)\).

3. Conclusion:

The coordinates of the image \(D^{\prime}\) after reflecting point \(D\) \((a, b)\) over the line \(y = x\) are \((b, a)\).

Thus, the correct answer is:
[tex]$[tex]$\boxed{(b, a)}$[/tex]$[/tex]