Angel Sum Property of Triangle
Three angles of a triangle are formed at each vertex by a pair of adjacent sides. The sum of measures of these three angles of any triangle is invariably equal to the straight angle, also expressed as 180°, π radians, two right angles, or a half-turn.
To teach sum of 3 angle of triangle is 180. This manipulative provided with cutout of angles from triangle. Provided with magnet at back to demonstrate on magnetic board.