Urgent please help..

Answer:
a = 17[tex]\sqrt{2}[/tex]
Step-by-step explanation:
Using the sine ratio in the right triangle and the exact value
sin45° = [tex]\frac{1}{\sqrt{2} }[/tex] , then
sin45° = [tex]\frac{opposite}{hypotenuse}[/tex] = [tex]\frac{17}{a}[/tex] = [tex]\frac{1}{\sqrt{2} }[/tex] ( cross- multiply )
a = 17[tex]\sqrt{2}[/tex]