Answer:
The 2nd one
Step-by-step explanation:
The ratio of the sides of 45-45-90 triangles is a:a:a[tex]\sqrt{2}[/tex]. 9 would be the side that is equal to a[tex]\sqrt{2}[/tex], so to find what a is you have to do 9 divided by [tex]\sqrt{2}[/tex]. The way you do this is make it the fraction [tex]\frac{9}{\sqrt{2}}[/tex] and multiply that by [tex]\frac{\sqrt{2}}{\sqrt{2}}[/tex] so you would get [tex]\frac{9\sqrt{2}}{2}[/tex], which is the second one
