Answer:
[tex]\sqrt{10}[/tex]
Step-by-step explanation:
Let the third side be x
Using Pythagoras' identity on the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
x² + 9² = ([tex]\sqrt{91}[/tex])², that is
x² + 81 = 91 ( subtract 81 from both sides )
x² = 10 ( take the square root of both sides )
x = [tex]\sqrt{10}[/tex]
