Question

to prove the angle sum properties of a triangle​

Answer 1

Answer:

To prove the above property of triangles, draw a line \overleftrightarrow {PQ} parallel to the side BC of the given triangle. Thus, the sum of the interior angles of a triangle is 180°

Answer 2

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Step-by-step explanation:

Take a cardboard of suitable size and by using adhesive, paste a white chart paper on it.

Draw a ΔABC of suitable lengths on the drawing sheet and also mark all the angles as shown in Fig. 12.2.

By using tracing paper, cut out the angles respectively equal to ∠A , ∠B and ∠C from a drawing sheet, (see Fig. 12.3).

Now, draw a line on the cardboard and paste the cut outs of the angles (∠A, ∠B and ∠C) on the line at a point O as shown in Fig. 12.4.