+130516 The diameter is twice the radius.....however.....if you're asking how to construct a diameter in a circle, here's one way using Euclid's simple method for finding the center of a circle.....the line CE that bisects the chord AB at right angles is a diameter........
http://aleph0.clarku.edu/~djoyce/java/elements/bookIII/propIII1.html
+130516 The diameter is twice the radius.....however.....if you're asking how to construct a diameter in a circle, here's one way using Euclid's simple method for finding the center of a circle.....the line CE that bisects the chord AB at right angles is a diameter........
http://aleph0.clarku.edu/~djoyce/java/elements/bookIII/propIII1.html
