Question

question 15 of 25
a______ has two - fold rotational symmetry.
a. equilateral triangle
b. line
c. circle
d. square

Explanation:

• Equilateral triangle: It has three - fold rotational symmetry. When rotated by \(120^{\circ}\) (\(\frac{360^{\circ}}{3}\)), it looks the same.
• Line: A line has infinite - fold rotational symmetry. Rotating a line by any angle around its mid - point (in 2D) or its axis (in 3D) leaves it unchanged.
• Circle: A circle has infinite - fold rotational symmetry. Rotating a circle by any angle around its center leaves it unchanged.
• Square: A square has four - fold rotational symmetry. But if we consider the non - full rotational symmetries, when we rotate a square by \(180^{\circ}\) (\(\frac{360^{\circ}}{2}\)), it maps onto itself. So, a square has two - fold rotational symmetry (in addition to four - fold).

Answer:

D. square