"Arc Length and Sector Area" Circle PPT (Second Lesson)

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"Arc Length and Sector Area" Circle PPT (Second Lesson)

The first part: the famous teacher’s eye-catching

Knowledge point 1: Generatus and height of cone

A cone is a geometric solid surrounded by a base and a side. Among them, the line connecting any point on the circumference of the cone base and the vertex of the cone is called the generatrix of the cone; the line segment connecting the vertex of the cone and the center of the base is called the height of the cone.

Core tip: The generatrix passing through a point on the base circumference of the cone, the radius of the base circle passing through this point and the height of the cone form a right triangle.

Knowledge point 2: Side area and total area of ​​a cone

(1) Side area of ​​the cone: Suppose the length of the cone's generatrix is ​​l and the radius of the base circle is r, then its side area S side = 1/2l·2πr=πrl.

(2) The total area of ​​the cone: The total area of ​​the cone is the sum of its side area and base area, that is, S total = S side + S base = πrl + πr2 = πr (l + r).

Arc length and sector area PPT, Part 2 content: Basic pass

1. If the side expansion of the cone is a semicircle with radius a, then the height of the cone is ()

A. a B. √3/3a

C. √3a D. √32a

2. If the side area of ​​a cone is equal to 3 times the area of ​​its base, then the degree of the central angle of the sector corresponding to the side expansion of the cone is ()

A. 60°B． 90°

C. 120° D. 180°

3． The base radius r of the cone is 6 cm and the height h is 8 cm. Then the side area of ​​the cone is ()

A. 30π cm2 B. 48πcm2

C. 60π cm2 D. 80πcm2

4. [Guangxi High School Entrance Examination] As shown in the figure, in the fan-shaped OAB, the angle between the radius OA and OB is 120°, and the distance between point A and point B is 2√3. If the fan-shaped OAB happens to be the side expansion of a cone, then the The radius of the base of a cone is ______.

Arc length and sector area PPT, Part 3: Capacity improvement

7. "Catching tops" is a very popular sport. The figure below shows the three-dimensional structure of a top. It is known that the diameter of the base circle AB = 8 cm, the height of the cylinder part BC = 6 cm, and the height of the cone part CD = 3 cm, then the surface area of ​​this top is ()

A. 68π cm2 B. 74πcm2

C. 84π cm2 D． 100πcm2

8. As shown in the figure, cut out a sector ABC with a central angle of 90° from a circular iron sheet with a diameter of 2 meters (three points A, B, and C are on ⊙O), and surround the cut sector into the side of a cone. Then the radius of the base circle of the cone is ______ meters.

9. [Error-prone question] It is known that the side expansion of a cylinder is a rectangle with a length of 6π and a width of 4π, then the radius of the base circle of the cylinder is __________.

10. As shown in the figure, in Rt△ABC, ∠C=90°, AC=6, BC=8. Taking the straight lines of the two right-angled sides as the axes, rotate △ABC once and find the side area of ​​the resulting cone.

Arc length and sector area PPT, part 4: thinking training

13. [Core literacy question] As shown in Figure 1, the radius of the base of the cone is 1 and the length of the busbar is 4. Figure 2 is an expanded view of its side.

(1) Find the area of ​​the shaded part (retain π in the result);

(2) The bus line SC is a honey line. How far must an ant crawl from A along the cone surface to eat honey?

Keywords: Free download of PPT courseware for mathematics in the first volume of the ninth grade of the People's Education Press, download of arc length and sector area PPT, download of circle PPT, .PPT format;

For more information about the "Arc Length and Sector Area" PPT courseware, please click on the Circle PPT Arc Length and Sector Area PPT tab.

"Arc Length and Sector Area" Circle PPT (Lesson 1):

"Arc Length and Sector Area" Circle PPT (Lesson 1) Part One Content: Learning Objectives 1. Understand the process of searching for arc length and sector area formulas. (Difficulty) 2. Be able to use the calculation formulas of arc length and sector area to perform calculations .(Key point) ... ... ... Arc length and fan...

Download "Arc Length and Sector Area" Circle PPT:

"Arc Length and Sector Area" Circle PPT Download Part One: Thinking We know that an arc is a part of a circle, and the arc length is a part of the circumference of a circle. Think about it, how do you calculate the circumference of a circle with radius R? Circumference of a circle C = 2R How much can the circumference of a circle be considered...

"Arc Length and Sector Area" Circle PPT (First Lesson):

"Arc Length and Sector Area" Circle PPT (Lesson 1) Part One Content: Famous Teacher’s Key Knowledge Point 1 The arc length formula n is the arc length l subtended by the central angle of the circle. The calculation formula is l=nR/180, where R is the radius. ． Core tip: In the arc length formula, l, n, R are known...

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Update Time: 2024-10-03

This template belongs to Mathematics courseware People's Education Press Ninth Grade Mathematics Volume 1 industry PPT template

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