Multiple choice general knowledge math & puzzles How many sides a circle of radius R have? 2 TT R TT R*R 2 TT R*R none of these Reveal answer Fill a bubble to check yourself D Correct answer Explanation In Euclidean geometry, a circle is defined as a smooth curve with no straight sides (or infinitely many infinitesimal sides). None of the provided formulas (circumference or area) represent the 'number of sides'.