Question

Find by construction the centre of a circle, using only a 60-30 setsquare and a pencil

Answer 1

Step 1: Draw any circle of any radius.

Step 2: Place perpendicular vertex of the set square on any part of the circumference of the circle, and draw the rays along the perpendicular sides of set square such that they intersect the circle at point $A$ and $B$.

Step 3: Join $AB$.

Step 4: Repeat this process with now placing the perpendicular vertex of the set square on any other part of the circumference of the circle. Let the points be $C$ and $D$.

Step 5: Join $CD$

Step 6: The intersection of $AB$ and $CD$ gives the centre $O$ of the circle.