1, acute angle refers to an angle greater than 0 degrees and less than 90 degrees, and a triangle with three acute angles is an acute triangle. The sum of the two acute angles is not necessarily greater than the right angle, but it must be less than the right angle.

2. A right angle is an angle equal to 90 degrees, and a triangle with a right angle is a right triangle.

3. Oblique angle refers to an angle greater than 90 degrees and less than 180 degrees, which is called obtuse angle, and a triangle with obtuse angle is an obtuse triangle.

Acute angle: in architectural design, acute angle is often used in some corners or decorations of buildings, such as triangles and spires.

Obtuse angle: In mechanical design, obtuse angle design can reduce stress concentration and improve the strength and toughness of parts. For example, in aircraft wing design, obtuse angle design is usually used to reduce aerodynamic drag during flight.

Right angle: In mathematics, right angle is the basis of Pythagorean theorem, for example, in the calculation of trigonometric function, the existence of right angle is very important.

The different properties of acute angle, obtuse angle and right angle have great influence on geometry. For example, the classification of triangles depends on the size of their internal angles.

The properties of acute angle, obtuse angle and right angle also affect some important theorems in geometry, such as right angle in Pythagorean theorem and acute angle in trigonometric cosine theorem.

The function of triangle

1. engineering building: triangular structure is widely used in engineering. Many buildings are triangular structures, mainly with good stability, which is not as easy to deform as quadrangles, and has the characteristics of stability and firm compression.

2. Traffic warning signs: Traffic warning signs are usually triangular and set on both sides of the road to play a warning role.

3. Daily life: Triangle is also widely used in daily life. For example, cut watermelons are usually triangular. In addition, the shape of clothes hangers is usually triangular.

4. Musical instrument: Triangle iron is an ancient percussion instrument, which is indispensable in wind bands, orchestras, symphonies and even bands. Performance is often added to colorful paragraphs to enhance the atmosphere.