How do you calculate the area of a circle? How to calculate the area of a circle

s r s = area.

r=radius. The length of the rectangle is equal to half the circumference of the circle. Namely. The width of the r rectangle is equal to the radius r of the circle.

Because the area of the rectangle is long and wide.

So. The area of the circle r r

r Based on the area formula of the circle that we have just deduced from converting the circle into a rectangle, students think about it, can we convert the circle into other shapes to derive the area formula of the circle?

4. Summarize the area formula of the circle.

s r s r s = area.

r=radius. The length of the rectangle is equal to half the circumference of the circle. Namely. The width of the r rectangle is equal to the radius r of the circle.

Because the area of the rectangle is long and wide.

So. The area of the circle r r

r Based on the area formula of the circle that we have just deduced from converting the circle into a rectangle, students think about it, can we convert the circle into other shapes to derive the area formula of the circle?

4. Summarize the area formula of the circle.

s＝πr²

How to calculate the area of a circle.

How to calculate the area of a circle. Good 50 points.

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s r s = area.

r=radius. The length of the rectangle is equal to half the circumference of the circle. Namely. The width of the r rectangle is equal to the radius r of the circle.

Because the area of the rectangle is long and wide.

So. The area of the circle r r

r Based on the area formula of the circle that we have just deduced from converting the circle into a rectangle, students think about it, can we convert the circle into other shapes to derive the area formula of the circle?

4. Summarize the area formula of the circle.

s＝πr²

The area of the circle is equal to the square of the radius multiplied by one-half of the diameter.

The formula for the area of a circle is: s= r, s= (d 2), d is the diameter, r is the radius, is the pi, usually taken, the formula of the area of the circle is constantly deduced by ancient mathematicians.

Zu Chongzhi, an ancient mathematician in China, started from the regular hexagon inside the circle, multiplied the number of sides, and used the area of the circle to approximate the area of the circle with the regular polygon.

The ancient Greek mathematicians started from the circle with regular polygons and tangent regular polygons at the same time, increasing the number of their sides, and approximating the area of the circle from both the inside and outside.

Mathematicians in ancient India used a method similar to cutting a watermelon, cutting a circle into many small petals, and then docking these small petals into a rectangle, and replacing the area of the circle with the area of the rectangle.

Kepler, a German astronomer in the 16th century, divided the circle into many small sectors; The difference is that he begins by dividing the circle into infinitely many small fan-shapes. The area of the circle is equal to the sum of the areas of an infinite number of small sectors, so in the last formula, the sum of the small arcs of the segments is the circumference of the circle 2 r, so there is s= r.

1. The area of the semicircle: s semicircle = (r 2) 2. (r is the radius).

2. The area of the ring: S big circle - S small circle = (r 2-r 2) (r is the radius of the large circle, r is the radius of the small circle).

3. The circumference of the circle: c=2 r or c=d. (d is the diameter, r is the radius).

4. The circumference of the semicircle: d+(d) 2 or d+ r. (d is the diameter, r is the radius).

5. The length of the arc of the sector l=the central angle (radian system) r= n r 180. ( is the central angle of the circle) (r is the radius of the fan).

6. Sector area s=n r 360=lr 2. (l is the arc length of the fan).

7. The radius of the bottom surface of the cone r=nr 360. (r is the base radius) (n is the central angle).

is the sum of an infinite number of small sector areas, so in the last formula, the sum of the small arcs of the segments is the circumference of the circle 2 r, so there is s = r.

The area of the circle is based onAxiom: "The area of the circle is deformed by softening equal area."(Circle to Square).is seven-ninths of the area of its inscribed square.", launchedTheorem:"The area of a circle s is equal to seven times the square of one-third of its diameter d"Area formula for a circle:

s=7(d/3)²。

Knowing the method of finding the area of the circumference of a circle, let the radius be r, then the circumference is 2 r, so the perimeter of r is 2. So the area r perimeter 2 ) perimeter 4 ) perimeter 4 .

The width of the rectangle is equal to the radius of the circle (r), and the length of the rectangle is half the circumference of the circle (c).

The area of the rectangle is ab, and the area of the circle is the square of the radius (r) of the circle multiplied by .

The area of the circle = pi and the square of the radius, the letter indicates: s = r.

1. Circle area: s= r, s= (d 2). (d is the diameter, r is the radius).

2. The area of the semicircle: s semicircle = ( r 2) 2. (r is the radius).

3. The area of the circle: S large circle - S small circle = (r 2-r 2) (r is the radius of the large circle, r is the radius of the small circle).

4. The circumference of the circle: c=2 r or c=d. (d is the diameter, r is the radius).

5. The circumference of the semicircle: d+(d) 2 or d+ r. (d is the diameter, r is the radius).

The area of the circle: s circle = multiplied by r squared; Formula: s= r.

Trigonometric functions can be used to calculate.

Knowing an angle can find out the sine value and cosine value of the angle, and thus the length of each side can be inferred.

Special angles such as 30°, 45°, 60°, 90° can be found directly.

Trigonometric function is one of the basic elementary functions, which is a function in which the angle (the most commonly used radian system in mathematics) is the independent variable, and the angle corresponds to the coordinate of the terminal edge of any angle and the intersection point of the unit circle or its ratio as the dependent variable. It can also be defined equivalently in terms of the length of the various line segments related to the unit circle. Trigonometric functions play an important role in the study of the properties of geometric shapes such as triangles and circles, and Souchai is also a fundamental mathematical tool for the study of periodic phenomena.

In mathematical analysis, trigonometric functions are also defined as infinite series or solutions to specific differential equations, allowing their values to be extended to arbitrary real values, even complex values.