This practice is designed to show how to mark 60° , 30° and 15° angles. You can mark any of these angles from a straight line using a compass and starting with a 60° angle.

**First:** Draw a straight line of any length and mark

a point on the line close to the center. Set your

compass point on the marked point and draw

a semi-circle or half of a circle.

**Second:** Leave the setting of the compass the

sameas above and place the compass point where

the semi-circle and the straight line meet. Mark a

small arc across the semi-circle.

**Third:** Draw a line from the center point

of your straight line to the mark on the semicircle.

The line is 60° from the bottom line.

To mark a 30° angle, divide the sixty degree angle in half ( bisect the angle). Since all points on the semi-circle are equal distance from the center, all you have to do to bisect the angle is:

**First:** Keep your compass setting the same

and place the compass on the point where

the semi-circle and one of the straight lines

of the 60° angle meet. Mark an arc above,

but within the boundaries of the 60° angle.

Repeat the same action for the other 60° angle line.

**Second:** Draw a straight line from the center

point of the straight line (vertex of the 60° angle)

to where the arcs cross. This causes the 60° angle

to be bisected and results in two 30° angles.

To mark a 15° angle, keep the compass setting the same and bisect one of the 30° angles.