It is possible to calculate corner degree, having applied Pythagorean theorem and having used "Four-digit mathematical tables" of Bradis. Such calculation is possible for finding of acute angles of a triangle. How to make it?

## Instruction

1. To calculate the size of an acute angle in a rectangular triangle, it is necessary to know values of sizes of all its parties. Accept necessary designations for elements of a rectangular triangle: c – hypotenuse; a, b are legs; A – An acute angle which is opposite to b leg; B – An acute angle which is opposite to a leg.

2. Count length of that party of a triangle which is unknown, applying for this purpose Pythagorean theorem. If the leg - and and a hypotenuse - c is known, then it is possible to calculate a leg - b; for what subtract from a hypotenuse length square about a leg length square - a, then take a square root from the received value.

3. In the similar way it is possible to calculate a leg if the hypotenuse of c and a leg - b are known, for this purpose with subtract a leg square from a hypotenuse square - b. After that take a root from the received result square. If two legs are known, and it is necessary to find a hypotenuse, put squares of lengths of legs and take a square root from the received value.

4. On a formula for trigonometrical functions calculate A sine of the angle: sinA=a/c. In order that the result was more exact, use the calculator. Round the received value to 4 signs after a decimal comma. Similarly find B sine of the angle for what sinB=b/c.

5. Using "Four-digit mathematical tables" of Bradis, find values of corners in degrees on the known values of sine of these corners. For this purpose open table VIII of "Tables" of Bradis and find in it value of the sine calculated earlier. In this line of the table in the first column "A" the value of a required corner in degrees is specified. In a column where there is a value of a sine, in the top line "And", find value of minutes for a corner.