Question

root 8 on number line

Answer 1

Draw a right angle triangle of sides AB = 2 and  BC = 2. The hypotenuse AC will be of length sqroot(8).  Use the proper procedure to draw  BC perpendicular to AB (like perpendicular bisector).

Now from A draw an arc of radius AC, to cut  the extended AB at D.  

AD = sqroot 8.