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

Description

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

Part One: 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 calculate. (Key point)

Arc length and sector area PPT, part 2 content: introducing new lessons

Situation introduction

Question 1 As shown in the picture, in the 4×100 meter race at the sports meeting, A and B are on the 1st track and the 2nd track respectively. Why are their starting lines not at the same place?

Question 2 How to calculate the "straightened length" of a curve?

Arc length and sector area PPT, part 3: teaching new lessons

Calculations related to arc length

collaborative inquiry

Question 1 What is the circumference of a circle with radius R?

Question 2 In the figure below, what fraction of the arc length is the length of the arc subtended by the central angle of each circle in the figure below?

Key points of knowledge

arc length formula

When calculating using the arc length formula, pay attention to the meaning of n in the formula. n represents a multiple of the central angle of 1°, which has no unit.

Do the math: It is known that the central angle subtended by the arc is 60° and the radius is 4, then the arc length is ____.

Example 1 When manufacturing a curved pipe, first calculate the "straightened length" according to the center line, and then cut the material. Try to calculate the straightened length l. of the pipe shown in the figure (unit: mm, accurate to 1mm)

Calculations related to sector area

concept learning

The figure enclosed by an arc of a circle and two radii passing through the endpoints of this arc is called a sector.

As shown in the figure, the yellow part is a fan shape, which is recorded as fan-shaped OAB.

collaborative inquiry

Question 1 What is the area of ​​a circle with radius r?

Question 2: What fraction of the area of ​​each sector in the figure below is the area of ​​the circle? What is the specific area?

Arc length and sector area PPT, Part 4: Practice in class

1. It is known that the circumferential angle subtended by the arc is 90° and the radius is 4, then the arc length is _____.

2. As shown in the figure, in Rt△ABC, ∠C=90°, ∠A=30°, BC=2, O and H are the midpoints of AB and AC respectively, rotate △ABC clockwise 120° to △A1BC1 position, then the area swept by the line segment OH during the entire rotation is ( )

3. As shown in the figure, �A, �B, �C, and �D do not intersect each other, and the radii are all 2cm, then the area of ​​the shaded part in the figure is ______.

Arc length and sector area PPT, Part 5 content: Class summary

arc length

Calculation formula:

sector

definition

formula

Shaded area

Seeking the law: overall thinking

arcuate

formula

S arc=S fan-S triangle

S arc = S sector + S triangle

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.

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 (Second Lesson):

"Arc Length and Sector Area" Circle PPT (Second Lesson) Part One Content: Famous Teacher's Key Points Knowledge Point 1 The Generatus and Height of a Cone A cone is a geometric body 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...

"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: 2024-11-26

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

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