try to solve this mathway/symbolab is allowed :)

Show me a diagram of my hint.

Join the centre of the top right circle to the centre of the bottom left circle. You now have the hypotenuse of an isosceles right triangle. Find the length of the leg of that triangle and you should be good to go.

can you elaborate a bit more? That would be nice :)

Show me a diagram of my hint.

Join the centre of the top right circle to the centre of the bottom left circle. You now have the hypotenuse of an isosceles right triangle. Find the length of the leg of that triangle and you should be good to go.