How to Draw an Equilateral Triangle

There are several ways to draw an equilateral triangle in technical drafting:

Constructing an Equilateral Triangle from a Line Segment

One method is to start with a side of the triangle, that is, with a line segment AB.

a line segment labeled AB

Place the compass point on end A and draw an arc with a radius equal to the length of AB.

drawing the first arc with radius AB from center A

Without changing the compass width, place the compass on point B and draw a second arc.

drawing the second arc with radius AB from center B

The two arcs intersect at point C, which marks the third vertex of the equilateral triangle.

the vertex C of the triangle

All that’s left is to connect points A and C, and B and C, to complete the other two sides of the triangle.

the completed equilateral triangle

In an equilateral triangle, all three sides are congruent, meaning they’re exactly the same length.

Start by drawing a circle with center at point O and a radius of length r.

drawing a circle centered at O

Align your ruler horizontally on the page.

Then, using a set square placed perpendicular to the ruler, draw the vertical diameter AB.

drawing the vertical diameter AB

Next, place the compass point on B and, with a radius equal to OA, draw an arc that crosses the circumference.

This will locate points C and D.

drawing a semicircular arc from point A with radius OA

Points A, B, and C divide the circle into three equal arcs.

Now, draw the segments AC, AD, and CD to form the triangle.

an inscribed equilateral triangle

The final result is an equilateral triangle.

And so on.