### Theory:

Rough diagram:

Step 1: Draw the $$ΔABC$$ with the given measurements.

Step 2: Construct the perpendicular bisector of any two sides ($$AC$$ and $$BC$$) and let them meet at $$S$$ which is the circumcenter.

Step 3: $$S$$ as centre and $$SA = SB = SC$$ as radius, draw the circumcircle to passes through $$A$$, $$B$$ and $$C$$. Circumradius $$=$$ $$3.9 cm$$.