# Characteristics of triangles

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In this video I will explain **the characteristics of the triangles.**

I will explain the characteristics of the triangles within the **math:**

- The sum of two of its sides must always be greater than the third side.

- The value of the mean parallel of a triangle is the union of two midpoints of two sides.

- Triangles are the only polygons that are always convex. None of its three angles can be greater than 180º.

Theorems that can be applied in **right triangles** only:

- **Sine theorem: **The sides of a triangle are proportional to the sines of the opposite angles.

- **Cosine theorem**: the square of one side is equal to the sum of the squares of the two other sides minus twice the product of these last two sides and the cosine of the first opposite angle.

- **Pythagoras theorem**: the legs (a, b) hypotenuse (c). The hypotenuse squared is equal to the sum of its legs squared.

In the video you will see visual and graphic examples of these characteristics of the triangles so that you understand the points better. Also, if you want to practice what you learned in today's class, you can do the

**printable exercises with their solutions**that I have left you on the web.