This data sufficiency question presents the following situation: "Cars Y and Z travel side by side at the same rate of speed along parallel roads as shown above. When car Y reaches point P, it forks to the left at angle x°, changes speed, and continues to stay even with car Z as shown by the dotted line. The speed of car Y beyond point P is what percent of the speed of car Z?"
(1) The speed of car Z is 50 miles per hour.
(2) x = 45
The correct answer is B. I don't understand the solution pertaining to the second statement that explains how "(√2dz)/ry = dz/rz" converts into "ry = √2rz" Could you explain this relationship in more detail, please?