Answer:
y = 4[tex]\sqrt{5}[/tex]
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
y² = 8² + 4² = 64 + 16 = 80 ( take the square root of both sides )
y = [tex]\sqrt{80}[/tex] = [tex]\sqrt{16(5)}[/tex] = 4[tex]\sqrt{5}[/tex] ← exact value
