口語式短文：角度的測量

Measuring angles：

•  The math lessons in school have recently been teaching how to measure angles. Dad says that angle measurement is fundamental knowledge in geometry and trigonometry. I must fully comprehend it.

• 最近學校數學課教到角度的測量，爸爸說這是幾何學及三角學的基本常識，一定要弄清楚。

•  An angle is formed by two rays that have the same endpoint (or vertex). The magnitude of an angle is measured in degrees.

• 角是由從同一個頂點出發的兩條射線所構成的，角的大小是以度做為衡量單位。

•  A full circle is 360 degrees. A diameter is a straight line which cuts a circle in half. Therefore a straight line is 180 degrees. It is called a straight angle.

• 一個完整的圓周代表 360 度，直徑是一條把圓切成兩半的直線，因此一條直線代表 180 度，稱為平角。

•  A right angle is one fourth of a circle, so it is 90 degrees. Angles smaller than a right angle are called acute angles.

• 直角是四分之一個圓，所以是 90 度。比直角小的角稱為銳角。

•  Angles larger than a right angle but smaller than a straight angle are called obtuse angles. Angles larger than a straight angle but less than 360 degrees are called reflex angles.

• 比直角大、但比平角小的角稱為鈍角。大於平角、但不到 360 度的角稱為優角。

•  The sum of the measures of the three interior angles of any triangle is 180 degrees . So the interior angles of an equilateral triangle are all 60 degrees.

• 任何一個三角形的三個內角合計均為 180 度，所以等邊三角形的三個內角都是 60 度。

•  When two straight lines cross, four angles are formed. They can be grouped into two pairs of vertical angles. Vertical angles have equal measures.

• 兩條交叉直線會形成四個角，可分成兩組對頂角，每組對頂角的角度都相等。

•  We can use a protractor to measure angles. It is a transparent semicircular plastic disk marked with degrees.

• 我們可以用量角器來衡量角度的大小，它是透明、半圓形並且標有刻度的塑膠片。

•  The magnitudes of angles are usually measured anticlockwise. But a protractor usually has two sets of numbers representing clockwise and anticlockwise degrees. So it's very convenient for measuring angles.

• 角度的大小通常是以逆時針旋轉的方向來衡量，但量角器上面通常有順時針和逆時針兩種方向的刻度，所以測量起來很方便。

發表時間：2009/10/05 著作人：周國華老師