You will need
  • drawing a triangle;
  • - the range;
  • - protractor.
As a rule, the vertices of the angles of a triangle are denoted by capital Latin letters (A, B, C), and the opposite side of the small Latin letters (a, b, c) or by the names of the vertices of the triangle constituting that side (AC, BC, AB).
The sum of the angles of a triangle is 180 degrees. In a rectangular triangle, one angle (straight) will always be 90 degrees and the other acute, i.e. less than 90 degrees each. To determine the angle in a rectangular triangle is straight, measure with a ruler the sides of the triangle and determine the greatest. It is called the hypotenuse (AB) and is located opposite the right angle (C). The other two sides form a right angle are called legs (AC, BC).
When it is determined what the angle is sharp, you can either measure the angle with a protractor, or calculated using mathematical formulas.
To determine the measure of the angle with a protractor, align the top (let's denote it by the letter A) with a special mark on the ruler in the center of the protractor, the side AC must coincide with its upper edge. Note on the circular part of the protractor to the point, through which the hypotenuse AB. The value at this point corresponds to the angle in degrees. If the protractor provided (2) the values for acute angle need to choose smaller, for the stupid - big.
The angle can be calculated by making simple mathematical calculations. You will need a basic knowledge of trigonometry. If you know the length of the hypotenuse AB and leg sun, calculate the value of the sine of the angle A: sin (A) = BC / AB.
The resulting value find the reference tables Bradis and determine what angle corresponds to the obtained number. This method was used by our grandmothers.
In our time, it is sufficient to take the calculator with the function of calculating trigonometric formulas. For example, the built-in Windows calculator. Run the application "Calculator" in the menu "View" select "Engineering". Calculate the sine of the desired angle, for example, sin (A) = BC/AB = 2/4 = 0.5
Switch calculator mode to inverse functions, click INV on the scoreboard calculator, then click calculate arcsine functions (on the scoreboard indicated, as sin to the minus one). In the window calculation will appear the following inscription: asind (0.5) = 30. I.e., the value of the desired angle of 30 degrees.