Drawing triangles

Drawing triangles with a compass and a rule is shown in the figure.

An equilateral triangle with side a is drawn in this way, that we measure segment AB on the straight line, equal to the side of a triangle. From points A and B, radius equal to the segment AB, we circle the arcs, which will intersect at point C. We connect point C with points A and B and thus we get an equilateral triangle (figure a).

To draw an isosceles triangle, you need to know the length of the base a and the side b. First we draw the base of the triangle AB equal to the given side a. From the points A and B of the base we circle the gaps (radius equal to the segment b), which will intersect at point C. We connect point C with points A and B and we get an isosceles triangle (drawing b).

Heterogeneous triangles can be drawn using a similar method; you need to know the dimensions of the three sides (drawing c) or two sides and one angle (drawing d), or one side and two angles.