Hi, given: a circle, radius = r; angle of one radian. - - - Radian https://en.wikipedia.org/wiki/Radian A radian on a circle has sides: a radius, a radius, an arc with length 1 radius. - - - (1) Area of the circle = π.r^2 A circle has 2.π. rad. If area of 1 radian angle =1 rad then (2) area of the circle = 2.π.rad (1), (2) => 2.π.rad = π.r^2 <=> 2. rad = r^2 The area of two radians makes (the area of) one square?