for √10, mark a point A on the number line such that OA = 3 and draw a line AB perpendicular to the number line such that AB = 1
= OB2= (3)^2 + (1)^2
=> OB = √10 (by pythagorus theorem)
With center at O and radius = OB = √10, cut an arc at C on the number line
=> OC = √10.