Semicircular circumference = ∏ r+2r;
2. In a rectangular flower bed 8 meters long and 6 meters wide, the largest flower bed was built. Peony flowers are planted in the annular flower bed, and jasmine flowers are planted outside the annular flower bed. What is the planting area of these two kinds of flowers?
Peony flower: (6÷2)? ×3. 14=28.26m? ;
Jasmine: 8× 6-28.26 = 48-28.26 =19.74m? .
3. The area of a circle is half of a semicircle, and the circumference of the circle is 18.84 cm. What is the circumference of a semicircle?
Circle radius =18.84 ÷ 3.14 ÷ 2 = 3cm;
Semicircular area =(3? ×3. 14)×2=56.52cm? ;
The square of the radius of the semicircle is 56.52 ÷ 3.14 =18; Radius = 3 √ 2 cm;
Semicircular circumference =3√2∏+6√2 (cm)