The type of right triangle here is the isosceles type
Thus, AB and BC are of the same length
We can call this x
Mathematically, according to Pythagoras' theorem, the square of the hypotenuse AC equals the sum of the squares of the two other sides in a right triangle
Thus, we have this as;
[tex]\begin{gathered} 30^2=x^2+x^2 \\ 2x^2\text{ = 900} \\ x^2\text{ = }\frac{900}{2} \\ \\ x^2\text{ = 450} \\ x\text{ = }\sqrt[]{450} \\ x\text{ = 15}\sqrt[]{2} \end{gathered}[/tex]