圆形Problems

area of a circle= TTr^2
circumference of a circle = 2TTr
The length of an arc of a circle is expressed in linear units of measurement such as inches, cm, and feet. Degrees are used to represent the measure of an arc. A degree is a unit of measurement obtained by dividing one complete revolution (that is, a circle) into 360 equal parts, and then referring to each part as a degree. A circle contians 360 degrees, so the measure of an arc of a circle must be some fractional part of 360 degrees.
Since the measure of a circle is 360 degrees, the measure of a semicircle is 180 degrees. An arc whose degree measure is less than 180 is called a minor arc. A major arc has a degree measure greater than 180 but less than 360.
Therefore, the arc length proportion is:
length of arc/circumference = degree of measure of arc/360 degree

Definitions of sector and segment of a circle:
A sector of a circle is a region of a circle bounded by two radii and the minor arc they determine.
A segment of a circle is a region of a circle bounded by a chord and the minor arc that it cuts off. Therefore:
Area of a sector/area of circle = n degree/360 degree

圓面積= πx r^2
圓要積= 2πr
r係半徑
Length of arc實係話如果有2個point係個circle上面
呢2個point沿住個圓形既長度
佢要乖番個度數over 360係因為如果果2個point拉番條線去個中心果陣
就會有個度數既
咁姐係果個arc既長度就佔左個成個circle長度既幾份之360
Sector都係一樣咁解
不過變左係個圓既面續唔係長度

sector就係圓形一part既面積
呢一part果2條邊一定要係個radius黎嫁

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