6.4 inches
Step-by-step explanation:
The corner makes a triangle:
We would be applying pythagoras' theorem:
Hypotenuse² = opposite² + adjacent²
opposite = adjacent = x
hypotenuse = 9 in
9² = x² + x²
9² = 2x²
81 = 2x²
81/2 = x²
40.5 = x²
square root both sides:
x = √40.5
x = 6.36
To the nearest tenth, it will be 6.4 inches