AN ANGLE OF 60
- On a given AB, construct an angle of 60 at A
- With centre A and any radius, draw an acr to intersect AB at C
- With centre C and the same radius, draw an arc to intersect the first arc at D.
- Draw a line through D to meet A
- Angle DAB is the required angle.
AN ANGLE OF 90
- On a given line AB, construct a perpendicular at A
- With centre A and any radius, draw an arc to intersect AB at C
- With the same radius, starting at C, mark off 60 and 120 at D and E
- With centres D and E, strike arcs to intersect at F
- Draw a line through F to A. FA is perpendicular to AB
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