
How to construct an equilateral triangle, given one side?

1. 
 Start drawing a line segment between two given points, being one side of the triangle to be constructed.


2. 
 With the center at point 1 on the right, draw an arc of almost 90° upwards, passing through the other point 1, and therefore, with a radius equal to the length of the line segment.


3. 
 Repeat this for the point on the left. Both arcs must intersect.


4. 
 Draw the connecting line from point 1 on the left to the intersection of arcs 2 and 3.


5. 
 Draw the connecting line from point 1 on the right to the intersection of arcs 2 and 3.


6. 
 Lines 1, 4 and 5 together form the equilateral triangle to be constructed.

