How do you construct 90 degree?

Answer 1

1. Draw a line with points A and B
2. Take a compass, put the point on A and set it to greater than half of the line.
3. Draw a half circle intersecting AB
4. Keeping the same compass setting, put the point on B and draw another Half circle that crosses over the other circle.
5. Make the two points where the perimeter of the circles intersect, and label it DE
6. Draw a line that goes between D and E
7. Label the point where AB and DE interesect as C
8. Angles ACD, ACE, BCD, and BCE will be 90 degrees.