Determine the length of , given that and are two congruent right-angled triangles.
Step 1: Find the length of .
Corresponding sides of congruent triangles are equal in length, so the length of is equal to the length of .
Step 2: Find the length of .
Use Pythagoras' theorem, which states that the square of the length of a right-angled triangle's hypotenuse is equal to the sum of the squares of the lengths of the other two sides.
Substitute the known lengths in , and solve for the length of .