Constructing Straight Objects at Specific Angles

While you’re constructing a straight object, you can hold down the Shift key to make the object horizontal, vertical, or at an angle of 15º, 30º, 45º, 60º, or 75º. Construct the second point before you release the Shift key.

See also
Attaching a Straight Object to an Existing Object
To Construct a Line
To Construct a Ray
To Construct a Segment
How To Construct a Segment of Fixed Length
How To Construct an Angle of Fixed Measure