The equilateral triangle shown is rotated about line a. each side of the triangle measures 20 mm. what shape is created by the rotation and what is the approximate circumference of the base? circumference of a circle: c = 2πr

Measure of each side of equilateral triangle = 20 mm

When , we rotate the triangle about line a,which passes through mid point of any of three sides of equilateral triangle

We get the Shape of a Cone.

Distance from line a ,where it cuts one of sides of equilateral triangle to one of vertex of triangle= Radius of circle = 10 mm

→Circumference of a circle= 2 π r

                  = 2 × 3.14 × 10

                   =6.28 × 10

                    = 62.8 mm

                    = 63 mm (Approximately)