如何判断三角形的角是锐角还是钝角？
几何一直是古代历史和现代世界的一部分。目前几何学被用于设计、建筑工程、建筑材料的选择等。它同样是技术世界的一部分，因为几何被用于计算各种设计、制造、创建蓝图、编程等。
Geometry is a study of mathematics that deals with the study of shapes and their properties. The term is was derived from Greek words ‘ge’ and ‘materia’ which means earth and measurement respectively.
从以非常具体的方式使用各种形状，可以在他们的建筑和古代建筑作品中观察到早期的几何方法。
角度
角度可以定义为在某一点相交的两条相交线之间的空间。角的组成部分包括两个称为角边的臂和一个角形成的交汇点，称为顶点。角度以度为单位测量，从 0 度到 360 度。
The first angle was supposed by Carpus of Antioch.
角度可以简单地定义为在两条相交射线的交汇点处形成的形状或空间。角度一词源自拉丁语“angulus”，意思是“一个角落”。
角度在测量的基础上分为不同的类型。
角度类型
| Angles | Description |
|---|---|
 Acute angle | The angle that measures less than 90 degrees is the acute angle. The degree always measures between 0 and 90. |
 Right angle | The angle that exactly measures 90 degrees is a right angle. It is also considered as a half straight angle as half of 180 degrees makes a right angle. |
 Straight angle | The angle that measures exactly 180 degrees is a straight angle. Straight angles form straight lines. The measure of straight angle can be positive or negative |
 Obtuse angle | The angle that measures more than 90 degrees and less than 180 degrees is an obtuse angle. The degree always lies between 90 degrees and 180 degrees. |
 Reflex angle | The angle that measures more than 180 degrees and less than 360 degrees is the reflex angle. The degree always lies between 180 degrees and 360 degrees. |
如何判断三角形的角是锐角还是钝角？
回答：
If a triangle does not have a specific mention of a right angle. Then, we can determine if a triangle is acute, right, or obtuse by using the converse Pythagorean theorem.
As if the sum of the square of the two shortest sides of a triangle is greater than the square of the longest side. The triangle is an acute triangle.
a2+b2>c2
Let’s see this with a mathematical example.
Here,
=>a2+b2=(10)2+(12)2
=>a2+b2=100+144
=>a2+b2=244
=>c2=(15)2
=>c2=225
Since 244>225, and by the relation a2+b2>c2 the given triangle is acute.
Similarly, if the sum of the square of the two shorter sides of a triangle is smaller than the square of the longest side. The triangle is an obtuse triangle.
a2+b2
Here,
=>a2+b2=(4)2+(3)2
=>a2+b2=16+9
=>a2+b2=25
=>c2=(8)2
=>c=64
Since, 64>25, and by the relation a2+b2
示例问题
问题 1. 什么是钝角三角形？
回答：
An obtuse triangle is a triangle that has one obtuse angle (greater than 90°) and two acute angles.
问题2. 一个锐角三角形有几个锐角？
回答：
In an acute-angled triangle all the three internal angles of the triangle are acute, that is, they measure less than 90°.
问题 3. 一个三角形可以有多个钝角吗？
回答：
No, it is not possible for a triangle to have more than one obtuse angle. As the sum of a triangle equals to 180 degrees then, if one of the angles is obtuse the other has to be acute angles.