Answer: Choice D
![(9√(2))/(2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/3z8gg53b2llawbl5hzzkf5gnoxb6de7dot.png)
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Step-by-step explanation:
We have a 45-45-90 triangle. If x is the leg length, then y = x*sqrt(2) is the hypotenuse.
Solving for y gets us
![x= (y)/(√(2)) = (y√(2))/(2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/clmrdelee2xjxwnfh4okw9ubmpsam3ecly.png)
In this case, y = 9 is the hypotenuse which then leads to choice D.
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Another way to find the answer is to use the pythagorean theorem
a = x and b = x are the two congruent legs
c = 9 is the hypotenuse
Solving a^2+b^2 = c^2, aka x^2+x^2 = 9^2, will lead to
![x = (9√(2))/(2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/v4tzzcunm68nazsgv4amiqzw4f362znist.png)