Answer:
AC = units²
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse AC is equal to the sum of the squares on the other 2 sides, that is
AC² = AB² + BC² = 5² + 8² = 25 + 64 = 89 ( take square root of both sides )
AC = ≈ 9.43 ( to 2 dec. places )