The triangle is "right-angled", which means the length of the hypotenuse is the longest.
Again, it is an isosceles triangle, therefore it'll have two sides equal.
Therefore, except the hypotenuse, the two other sides are equal.

We use pythagoras theorem here because it's a right-angled triangle.
a² + b² = c²

c is the hypotenuse and,
a and b are the two other sides.

We can use a common letter for both sides, say, a.

The equation becomes,
a² + a² = c²
2a² = 4²
2a² = 16
a² = 8                            (dividing through by 2)
a = √8
a = 2.828427125
a ≈ 2.8 to 2 significant figures
2 5 2
The Brainliest Answer!
A square+ a square=c square
2a square = 4a square 
2a square = 16
a square = 8
a = root 8
a = 2.828427125
A=2.8 to 2 significant figures
2 3 2
So back of
My goodness! so you had to edit your answer after I solved hen? This site disgusts me; admins registering as users to create an impression.
But you copied foolishly, I never wrote 4a square, but in your haste, you wrote that.
Yeah yeah no one cares
By the way I knew it