What is the equation of the circle?

x² + y² = 3

Step-by-step explanation:

The equation of a circle centred at the origin is

x² + y² = r² ( where r is the radius )

Using Pythagoras' identity in right triangle CRT

CR² = 1² + ( )² = 1 + 2 = 3 ( take the square root of both sides )

CR = r = , then

x² + y² = ( )² , that is

x² + y² = 3