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.

Solution:

It is given that

Each side of equilateral triangle = 20 mm

When the triangle is rotated about the line ‘a’ that passes through the midpoint of any three sides of the equilateral triangle we obtain a cone shape.

The distance from the line a which cuts one side of a triangle to one vertex of the triangle is the radius = 10 mm

We know that

Circumference of a circle = 2 π r

Substituting the values

= 2 × 3.14 × 10

By further calculation

= 6.28 × 10

= 62.8 mm

= 63 mm

Therefore, the approximate circumference of the base is 63 mm.

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.

Summary:

The equilateral triangle shown is rotated about line a. Each side of the triangle measures 20 mm. The shape created by the rotation is a cone and the approximate circumference of the base is 63 mm.