Answer:
7
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
let the third side be x , then
x² + (4[tex]\sqrt{2}[/tex] )² = 9²
x² + 32 = 81 ( subtract 32 from both sides )
x² = 49 ( take the square root of both sides )
x = [tex]\sqrt{49}[/tex] = 7
Then the third side is 7
