This should be an example in the textbook. Your teacher will also give you a demonstration when giving lectures.

As shown in the figure, the length of the assembled approximate rectangle is about half of the circumference, and the width is about the radius.

It is known that the length of this rectangle is 6.28 cm.

Namely: πr=≈3. 14r=6.28.

r=2

What is the width of the rectangle? 2? centimetre

Area of circle = π r&; sup2≈3. 14×2 & amp； Sup2= 12.56 (square centimeter)