From the school planimetry course is knownDefinition: a triangle is a geometric figure consisting of three points that do not lie on one line, and three segments that pair these points in pairs. Points are called vertices, and segments? Sides of the triangle.
Separate the following types of triangles: acute, obtuse and rectangular.
Also, triangles are classified on the sides: Isosceles, equilateral and versatile. Depending on the type of triangle, there are several ways to determine its angles, sometimes it is sufficient to know only the shape of the triangle.
A triangle is said to be rectangular if it has a right angle. When measuring its angles, you can use trigonometric calculations.
In this triangle, the angle? C = 90?, As a straight line, knowing the lengths of the sides of the triangle, the angles? A and? B are calculated by the formulas: cos? A = AC / AB, cos? B = BC / AB. Degree measures of angles can be learned by referring to the cosine table.
A triangle is said to be equilateral if it has all sides equal.
In an equilateral triangle, all angles are 60 ?.
In the general case, to find the angles in an arbitrary triangle, one can use the cosine theorem
Cos ?? = (B? + C? - a?) / 2? B? C
The degree of the angle can be determined by referring to the cosine table.
A triangle is said to be isosceles if it has two sides equal, a third side is called the base of the triangle.
In an isosceles triangle, the angles at the baseAre equal, i. ? A =? B. One of the properties of a triangle is that the sum of its angles is always 180 ?, therefore, computating by the cosine theorem the angle? C, the angles? A and? B can be calculated as follows:? A =? B = (180? -?) / 2