CTET 2 Math and Science 27 Dec 2021 Paper

To prove the angle sum property of triangles, a mathematics teacher has distributed different types of triangles to the students. They were asked to measure the angles of triangles they have received. The teacher asked one of the students to consolidate the data on a chart paper in the following way
∠1 = 
∠2 = 
∠3 = 
∠1 + ∠2 + ∠3 = 
The method used by the teacher is