Circle area formula, circle length formula

Circle area formula, circle length formula

Answer: S = π R ^ 2, C = π D, where R is radius, D is diameter, s is area and C is perimeter
Area of circle = square of radius × π = R & # 178; π
Circumference of circle = diameter × π = R π = 2R π
When deducing the formula for calculating the area of a circle, the circle is divided into several parts to form an approximate rectangle. It is known that the length of the rectangle is 6.42cm more than the width, and the area of the circle is calculated
A good man, do me a favor,
1. In the derivation of the formula for calculating the area of a circle, the circle is divided into several equal parts to form an approximate rectangle. It is known that the length of the rectangle is 6.42 cm more than the width. What is the area of the circle? 6.42 ÷ (3.14-1) = 33 × 3 × 3.14 = 28.262
The length of the rectangle is half of the circumference of the circle, and the width is the radius. If the radius is r, then the half circumference is 3.14r, so 3.14r = R + 6.42, r = 3, and the area is 9 * 3.14 = 28.26 square centimeters
It should be 28.26 square centimeters
28。 Twenty-six
If the cut circle is spliced into a square, the short side of the rectangle should be the radius of the circle, and the long side is half of the circumference
So, let the radius of the circle be r, then the circumference of the rectangle = 2 * pi * r + 2 * r
If the circumference of the rectangle is 6.42cm more than the circumference, then 2 * r = 6cm, r = 3cm
Long side of rectangle = pi * r = 3.14 * 3 = 9.42cm
Rectangle short side = r = 3cm
Rectangle area = 9.42 * 3 = 28.26 square centimeter
If the cut circle is spliced into a square, the short side of the rectangle should be the radius of the circle, and the long side is half of the circumference
So, let the radius of the circle be r, then the circumference of the rectangle = 2 * pi * r + 2 * r
If the circumference of the rectangle is 6.42cm more than the circumference, then 2 * r = 6cm, r = 3cm
Long side of rectangle = pi * r = 3.14 * 3 = 9.42cm
Rectangle short side = r = 3cm
Rectangle area = 9.42 * 3 = 28.26 square centimeter
6.42÷（3.14-1）=3
3×3×3.14=28.26
In deriving the area formula of a circle, the circle is divided into several equal parts to form an approximate rectangle. It is known that the length of the rectangle is 10.70 cm more than the width, and the area of the circle is______ Square centimeter
Let the radius of a circle be r, then its perimeter is 2 π R. from the meaning of the title, we can get: 2 π R △ 2-r = 10.70, & nbsp; & nbsp; & nbsp; & nbsp; π R-R = 10.70, (π - 1) r = 10.70, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; r = 10.70 △ 3.14-1, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; r = 10.70 △ 2.14, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; r = 10.70 △ 2.14; R = 5; s = π R2, = 3.14 × 52, = 3.14 × 25, = 78.5 (square centimeter); answer: the area of a circle is 78.5 square centimeter
In the derivation of the area formula of a circle, the circle is divided into several equal parts to form an approximate rectangle
Let R be the radius of the circle
2*3.14*r+2*r＝16.56
R = 2 cm
The circumference is 3.14 * 2 * 2 = 12.56 cm
The circle area is 3.14 * 2 * 2 = 12.56 square centimeter
16.56 ﹣ 2 ﹣ 3.14 + 1 = 2 cm radius
Perimeter: 3.14 × 2 × 2 = 12.56 cm
Area: 3.14 × 2 & # 178; = 12.56 square centimeter
In deriving the area formula of a circle, the circle is divided into several equal parts to form an approximate rectangle. It is known that the circumference of the rectangle is 6cm more than that of the circle, and the area of the circle is______ cm2．
2, = 3.14 × 32, = 3.14 × 9, = 28.26 (square centimeter); answer: the area of this circle is 28.26 square centimeter
The formula for calculating the area of a circle is usually derived by using the______ To make the circle approximate to______ It's the length of a circle______ The width is equal to that of a circle______ So the area formula of a circle is expressed in letters as______ .
According to the analysis, the calculation formula of the area of a circle is usually deduced by using the cutting and splicing method, so that the assembled circle is similar to a rectangle, its length is equivalent to half of the circumference of the circle, and its width is equivalent to the radius of the circle, so the area formula of the circle is expressed by the letter π R2. So the answer is: cutting and splicing, rectangle, half of the circumference, radius, π R2
When deriving the area formula of a circle, divide the circle into several equal parts to form an approximate rectangle. Given that the circumference of the rectangle is 33.12 cm, what is the area of the circle in square cm?
Let the radius of a circle be r, then 2 × 3.14 × R + 2R = 33.12, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 8.28r = 33.12, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; r = 4, 3.14 × 42 = 50.24 (square centimeter); answer: the area of a circle is 50.24 square centimeter
Who can tell me the formula of area and perimeter of triangle, regular, long, circle and sector
C triangle = length sum of three sides
S triangle = (bottom * height on bottom) / 2
C trapezoid = length of each side added
S trapezoid = (upper bottom + lower bottom) * height / 2
C rectangle = (L + W) * 2
S rectangle = length * width
C square = 4 * side length
S Square = square of side length
C circle = 2 * 3.14 * radius or diameter * 3.14
S circle = 3.14 * square of radius
C sector = (degrees of center angle / 180 degrees) * 3.14 * sector radius
S sector = (degrees of center angle / 360 degrees) * 3.14 * square of sector radius
Rectangle C = (length + width) * 2
Rectangle s = length * width
Square C = side length * 4
Square s = side length * side length
C triangle = length sum of three sides
S triangle = (bottom * height on bottom) / 2
C square = 4 * side length
S Square = square of side length
C rectangle = (L + W) * 2
S rectangle = length * width
C circle = 2 * 3.14 * radius or diameter * 3.14
S circle = 3.14 * square of radius
C sector = (degrees of center angle / 180 degrees) * 3.14 * sector radius
S sector = (degree of center angle / 360 degree... Expansion)
C triangle = length sum of three sides
S triangle = (bottom * height on bottom) / 2
C square = 4 * side length
S Square = square of side length
C rectangle = (L + W) * 2
S rectangle = length * width
C circle = 2 * 3.14 * radius or diameter * 3.14
S circle = 3.14 * square of radius
C sector = (degrees of center angle / 180 degrees) * 3.14 * sector radius
S sector = (degrees of center angle / 360 degrees) * 3.14 * square of sector radius
C trapezoid = length of each side added
S trapezoid = (upper bottom + lower bottom) * high / 2 * folded
Circumference of triangle = sum of three sides
Triangle area = 1 / 2 bottom * height
Perimeter of square = sum of four sides
Square area = side length * side length
Circumference of rectangle = length × width
Circumference = diameter * 3.14
Circle area = R square
Sector perimeter = degree of center angle / 180 degrees) * 3.14 * sector radius
Sector area = (degrees of center angle / 360 degrees) * 3.14 * square of sector radius
Trapezoid perimeter = sum of four sides
Trapezoid area = (top bottom... Unfold)
Circumference of triangle = sum of three sides
Triangle area = 1 / 2 bottom * height
Perimeter of square = sum of four sides
Square area = side length * side length
Circumference of rectangle = length × width
Circumference = diameter * 3.14
Circle area = R square
Sector perimeter = degree of center angle / 180 degrees) * 3.14 * sector radius
Sector area = (degrees of center angle / 360 degrees) * 3.14 * square of sector radius
Trapezoid perimeter = sum of four sides
Trapezoidal area = (upper bottom + lower bottom) * height / 2 * retraction
There are three formulas for circle area, one for radius, one for diameter and one for circumference
I'm going to recite these formulas tonight. Come on, which expert told me that I'll be grateful to him all my life, and I'll offer a reward of 10 points. OK, 20 points
If the radius R is known, then the circle area s = π R & # 178;;
If the diameter D is known, then the circle area s = π (D / 2) & # 178; = π D & # 178 / 4;
If the circle length C is known, then the circle area s = π (C / 2 π) &# 178; = C & # 178; / (4 π)
A formula for finding the circumference (radius, diameter) of a given circle area,
Area of circle / 3.14 = square of radius
S = square of π R
The square of R = s / π
C=2πr=πd
S=πr^2
d=2r
Note: C perimeter, s area, R radius, D diameter
From the area of the circle s = Πr2, it can be concluded that:
R2=S/∏
So r = √ s / Π
The circumference of the circle L = 2 Π r = 2 Π * √ s / Π
Diameter = 2R = 2 * √ s / Π