How do you construct an angle of 90 degrees?

Answer 1

1. Draw a circle on a piece of paper.

2. Draw a straight line from the top center line of the circle to the bottom center line.

3. Draw a straight line from the left center line of the circle to the right center line.

These lines should form a plus sign (+). Place your pencil point in the center of the circle where the two straight lines meet. Your pencil point is at the corner of four equal 90 degree angles.

You can follow this method but it is inaccurate. A better way to construct a right angle is as follows:

1. Draw a straight line using a ruler
2. Use a pair of compasses to mark two arcs on the line that you have drawn
3. Place the compass point at the first point and adjust the compass so that the pencil goes just pass the point that you drew the first to lines
4. Draw a major arc across the line with the line roughly in the centre
5. Repeat for the second point, keeping the compass points the same distance apart
6. Join the two points where the arcs meet

You have bisected the line at the first point that you placed your compasses and have created four right angles.