Answer:
[tex]\text{One of the angles in the right triangle is already given as }45^\circ,\text{ so this is a}\\\text{right angled isosceles triangle. This means the sides of the triangle are }x,\ x\\\text{and }9.[/tex]
[tex]\text{Using pythagoras theorem,}\\9^2=x^2+x^2\\\\\text{or, }81=2x^2\\\\\text{or, }x^2=\dfrac{81}{2}\\\\\text{or, }x=\dfrac{9}{\sqrt2}\\\\\text{or, }x=\dfrac{9}{\sqrt2}\times\dfrac{\sqrt2}{\sqrt2}\\\\\text{or, }x=\dfrac{9\sqrt2}{2}[/tex]
