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Why is the side area of a cone π RL?
If the ground radius of the cone is r, the perimeter of the bottom surface is 2 π R
The arc length of the sector is also 2 π R, because its radius is L
So the center angle corresponding to the sector arc length is 2 π R / L
So the area is 2 π R / L * L ^ 2 / 2 = π RL
The diameter of circle a is 8 cm, which is two fifths of the diameter of circle B. what is the circumference of circle B?
If anyone did it before 6:30 p.m. on September 27,
20π cm
The circumference of a circle is 8 cm. What is its diameter?
Diameter 8 △ 3.14 ≈ 2.55cm
If you don't understand this question, you can ask,
The diameter of circle a is 8 cm, which is 40% of the diameter of circle B. the circumference of circle B is ()
62.8
The diameter of circle a is 8 cm, and the diameter of circle B is 5 / 2 of circle A. then, what's the circumference of circle B
The diameter is 8 × 5 / 2 = 20 cm
The circumference is 3.14 × 20 = 62.8 cm
2. A circle with a radius of 2 cm is equal to a circle with a diameter of 4 cm
A: these two judgments are correct!
If the diameter of the circle increases by 2 cm, then the circumference of the circle increases () if the radius of the circle increases
Diameter increases by 2, radius increases by 1, perimeter 2 * 1 * 3.14 = 6.28
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The radius of circle a is 2 cm, and the diameter of circle B is 3 cm. The ratio of circumference of circle a and circle B is (), and the ratio of area is ()
3÷2=1.5
Perimeter ratio = 2:1.5 = 4:3
Area ratio = 2 × 2:1.5 × 1.5 = 16:9
The total length of the circumference and diameter of a circle is 248.4cm. What is the radius of the circle?
Explain the solution and answer it before 7 a.m. tomorrow,
The sum of circumference and diameter of a circle is 248.4cm, that is 2 * 3.14 * radius + 2 * radius = 248.4cm
The circumference of a circle is 6.28cm, and its radius is______ Cm, the area is______ cm2．
It has a radius of 1 cm and an area of 3.14 square cm. So the answer is: 1, 3.14
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- 10. The proof of the formula of sector area! Let a sector radius be r and arc length be l, then the sector area s = 1 / 2lr. Why? Proof of the formula of sector area! Let a sector radius be r and arc length be l, then the sector area s = 1 / 2lr. Why? Proof!
- 11. Who can help me to deduce the formula of cone side area? Why is s = π RL?
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