What is a triangle?

Consider one of the simplest, and at the same time basic, geometry figures - a triangle. What is a triangle? This geometric shape is formed by three segments, called sides, which form three corners. In other words, a triangle is a kind of polygon that consists of exactly three corners. Depending on the size of the angles, as well as the aspect ratio, the following triangles are distinguished:

  • Equilateral
  • Isosceles
  • Rectangular
  • Angular
  • Obtuse
  • Versatile

About each of them in the order of presentation, we tell below.

Equilateral triangle

Equilateral triangle, what is it? From the point of view of solving problems, as well as mapping, an equilateral triangle is an “ideal” geometric figure. It is characterized by the equality of all three sides, as well as the equality of all angles, each of which is 60 degrees.

Isosceles triangle

What is an isosceles triangle? Compared with the previous type, this triangle has a certain similarity, namely.An equilateral triangle has two equal sides, as well as two equal angles at the base. This view is also useful when solving problems.

Right triangle

What is a right triangle? The right triangle is known for the Pythagorean theorem, which is very often used to find the sides of this triangle, and reads as follows: the square of the hypotenuse is equal to the sum of the squares of the legs (c2= a2+ b2). A hypotenuse of a right triangle is a side opposite to a right angle. The two remaining sides are called legs, which form a right angle (90 degrees).

Acute triangle

What is an acute triangle? The acute triangle, as the name implies, has three angles, each of which is less than 90 degrees, and form an acute angle. The lengths of the parties may be different.

Obtuse triangle

What is a obtuse triangle? A obtuse triangle is a triangle, one of the corners of which makes an obtuse angle, that is, more than 90 degrees. The remaining two will be necessarily sharp. The obtuse triangle cannot have two obtuse angles at the same time, otherwise it will degenerate.

Versatile triangle

What is a versatile triangle? Here we come to the most common type of triangles - versatile. The versatile triangle has three sides of different length, which make up three different angles of magnitude. Hand-draw a triangle without going into details, and you will most likely get a versatile triangle. This type is the most difficult when solving geometric problems.


The considered triangle has a similar form in the Lobachevsky geometry, considering the figures on the plane (school program). The sum of the angles of a triangle is always 180 degrees, under any circumstances. In a geometry that considers triangles on a sphere, the sum of the angles is larger in meaning, and the figures themselves have a slightly different appearance.

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