From a school course of planimetry the definition is known: a triangle is called the geometrical figure consisting of three points which are not lying on one straight line and three pieces which in pairs connect these points. Points call tops, and pieces – the parties of a triangle. Divide the following types of triangles: acute-angled, obtusangular and rectangular. Also triangles classify by the parties: isosceles, equilateral and versatile. Depending on a type of a triangle, there are several ways of definition of its corners, the nobility only a triangle form sometimes is enough.
Instruction
1. The triangle is called rectangular if it has a right angle. At measurement of its corners it is possible to use trigonometrical calculations. In this triangle a corner s = 90º as corners of ∠A and ∠B are calculated by a straight line, knowing lengths of the parties of a triangle, on formulas: cos∠A = AC/AB, cos∠B = BC/AB.-Degree measures of corners can be learned, having addressed the table of cosines.
2. The triangle is called equilateral if at it all parties are equal. All corners are equal in an equilateral triangle 60º.
3. Generally, for finding of corners in any triangle it is possible to use the theorem kosinusovcos ∠α = (b² + with² - a²) / 2 • b • sgradusnuyu the measure of a corner can be learned, having addressed the table of cosines.
4. The triangle is called isosceles if at it two parties are equal, the third party at the same time is called the triangle basis. Corners at the basis are equal in an isosceles triangle, i.e. ∠A = ∠B. One of properties of a triangle is that the sum of its corners is always equal 180º therefore having calculated according to the theorem of cosines a corner s, corners of ∠A and ∠B can be calculated so: ∠A = ∠B = (180º - s)/2