This invention relates to a device for visual understanding of geometrical theorems specifically the theorems relating to parallograms, rhombus, rectangle, square, trapezium and theorems relating to parallel lines intersected by a transversal. The device is provided on a smooth supporting sheet preferably acrylic and consists of four full scales joined together with nut and bolts to form a quadrilateral and two scales joined across the diagonals of quadrilateral. A full protractor with 0 to 360°C marking is provided at the intersection of the diagonals. Four semicircular protractors are provided at each of the vertices of the quadrilateral formed by the scales.
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