Divide a circle into 16 equal parts and form an approximate parallelogram (as shown in the figure below). The perimeter of the approximate parallelogram is 41.4. Find the area of the circle?

Divide a circle into 16 equal parts and form an approximate parallelogram (as shown in the figure below). The perimeter of the approximate parallelogram is 41.4. Find the area of the circle?

Let the radius of the circle be r and the circumference be 2 π R
Divide the circle into 16 parts, each part is an isosceles triangle,
The waist is the radius R and the bottom is 2 π R / 16 = π R / 8
The parallelogram is arranged by 16 triangles,
The circumference is (R + π R / 8 × 8) × 2 = 41.4,
∴r=5,
S=5²π=25π=78.5

When deducing the formula for calculating the area of a circle, divide a circle into 16 equal parts to form an approximate rectangular line. The width of the rectangular line is 3cm. What is the length of the rectangular line
What is the area of the circle

My junior high school
I haven't worked it out for a long time
Ask the teacher tomorrow

To deduce the area formula of a circle is to divide the circle into several equal parts and put them together into an approximate rectangle. It is known that the length of the rectangle is 64.2 cm more than the width and the area of the circle

πr-r=64.2
R = 64.2 △ 3.14-1 = 64.2 △ 2.14 = 30cm
Circular area π R & # 178; = 3.14 × 30 & # 178; = 1826 square centimeters

There is an isosceles triangle in the half of a circle. The area of the triangle is 10. What's the area of the circle? I'm a primary school student

There is an isosceles triangle in the half of a circle. The area of the triangle is 10
Then the height of the isosceles triangle is the radius R and the bottom is the diameter 2R
r*2r/2=10
r²=10
Circle area = π R & # 178; = 3.14 * 10 = 31.4