Triangle ABC is reflected across the line y = x. What are the coordinates of the vertex B' of the resulting triangle A'B'C'?
A. (2, -5)
B. (-2, 5)
C. (5, -2)
D. (-5, -2)

Length of CD = 9.8 units

Step-by-step explanation:

Given AB || CD

angles BAC = ACD ................alternate interior angles

Angles CBA = CAD = 90   (given)

=>

Triangles ABC and CAD are similar (AAA)

AB / AC = CA / CD   ................Similar triangles have corresponding sides proportional

5 / 7 = 7 / CD

CD = 7*7/5 = 49/5 = 9.8

=