How to calculate the perimeter area of a circle?

How to calculate the perimeter area of a circle?

The formula for calculating the circumference of a circle is: C = 2 π R. C represents the circumference of the circle, R represents the radius of the circle. The formula for calculating the area of the circle is: S = π R2 (the square of R). S represents the area of the circle, R is the radius of the circle

The circumference of a semicircle is equal to half the circumference of a circle of equal radius______ (judge right or wrong)

Because the circumference of a semicircle is equal to half the circumference of a circle plus its diameter, the circumference of a semicircle is not equal to half the circumference of a circle of equal radius

The result is lower than the original price. 2. The circumference of a semicircle is equal to half the circumference of a circle
3. A is an even number greater than 2, so it must be a composite number
4. The volume of a cylinder is equal to that of a cone. Given that the area of the bottom of the cone is 1 / 3 of the area of the bottom of the cylinder, the height of the cylinder is 1 / 9 of the height of the cone

The price of a commodity is increased by 10% and then decreased by 10%. The result is lower than the original price
The circumference of a semicircle is equal to half the circumference of a circle
3. A is an even number greater than 2, so it must also be a composite number. (T)
4. The volume of a cylinder is equal to that of a cone. Given that the area of the bottom of the cone is 1 / 3 of the area of the bottom of the cylinder, then the height of the cylinder is 1 / 9 of the height of the cone. (T) t is right, f is wrong