easy! that is a special triangle w/ angles 45-45-90 and sides x-x-
![√(x)](https://img.qammunity.org/2019/formulas/mathematics/college/kbjsziyl4peosfq0f23ijai585vpxo148c.png)
respectively
so, because u are given the
xs of the theory i explained you above (which in this case are "8"), u only have to plug in the 8 value into the square root.
this is because, again, the diagram is a special triangle which means its sides & angles are given *u can refer to the uploaded image's first triangle