The equilateral triangle shown is rotated about line a. Each side of the triangle measures 20 mm. What shape is created by the r
otation and what is the approximate circumference of the base? Circumference of a circle: C = 2πr a cylinder with a circumference of about 63 mm a cylinder with a circumference of about 126 mm a cone with a base circumference of about 63 mm a cone with a base circumference of about 126 mm
Rotating a triangle about a line results in a cone created by the rotation. This is because the segment at the bottom forms a circle, and the point at the top stays there; the three-dimensional figure with a circular base and a point at the top is a cone.
Since we rotate the segments about a line, this makes the length of the base the radius of the circle. This means the circumference would be
