Patent ID: 8371035

Claim:
A combination set of interacting instruments for construction and analyzing two dimensional mathematical figures, said combined set of interacting instruments comprising: a ruler, an adjustable triangle assemble with variable included angles, a compass and a protractor fixed to said ruler, and wherein; said ruler comprising an elongated strip of relatively rigid transparent plastic material having a length, width, and relatively thin thickness and said ruler defining a straight edge along one side of said width and extending along said length with units of length marked thereon, a pivot point in a generally middle portion of said ruler in which said pivot point extends through said ruler and includes a pointed end for anchoring said ruler and a pair of parallel longitudinally extending guideways and said ruler also including a third guideway parallel with said two guideways along the length of said ruler between said pivot point and one end thereof and a sliding positioning hole disposed in said third guideway for positioning a marking instrument rotatable about said pivot point to act as a compass; and in which said guideways in said ruler are slots extending through said ruler and said guide followers are relatively short pins that extend into said slots; a triangular assembly including two moveable elements for forming two sides of a triangle and having first and second ends with said two moveable elements pivotally connected together at one end of each of said moveable elements whereby said moveable elements are disposed in an end to end relationship with an included angle of up to 180° along said straight edge of said ruler and each of said two moveable elements including a guide follower at an opposite end from said pivot connection between said two moveable elements and said guide follower interacting with one of said two guideways in said ruler for forming a triangle with one side of said triangle formed by said straight edge of said ruler; and which includes a longitudinally extending slot in one of said moveable elements that extends from said pivotal connection between said two moveable elements along the length of said element for shortening one side of said triangle; and in which said triangular assembly is permanently connected to said ruler; and said protractor comprising a thin sheet of said transparent material having a flat base portion and an arcuate upper portion with angular indications between 0 and 180° on said base portion and said upper portion and said protractor including a pair of guide followers at opposite ends of said base portion for positioning said protractor on said ruler along the length thereof and for measuring the included angle between said ruler and each of said moveable elements; and in which said protractor includes three parallel arc shaped grooves in an upper portion thereof.