This computer is a special computer which calculates "neighboring length / height / angle / area" based on any triangular value. There are the two modes, the scalene triangle computer corresponding to a triangle at large and the right triangle computer which specialized in the right triangle. In scalene triangle computer mode, all other values are calculated by specifying three numerical values among "length / height / 3 the angle/areas of three sides." In right triangle computer mode, other values are calculated from two numerical values among "a base / oblique side / height / angle / area." Directions for use: An answer can be obtained only by carrying out a numerical input at an applicable item, and pushing a calculation button after choosing an input pattern.