Using the triangle solver App to sizes of a triangle can be calculated (up to ambiguities), where three determining factors are given. To be selected from the six pieces of the determination of a triangle (three sides and three angles) three (for example, the sides of a = 4 and b = 5, and the angle B = 60 °) is entered, and in the triangle-solvent App. Then an unknown quantity (eg, the angle A) and selected by means of the "Solve" button calculates its value (if one exists). At the same time the remaining unknown quantities are calculated. This process can be repeated as often as necessary, with the value of one or more variables can be amended or terminated by another variable.