Question

Proof for the sum of interior and exterior angle of nonagon by cutting and pasting method

Answer 1

Answer:

Materials Required

Cardboard sheet

Adhesive

Glazed papers

White chart paper

Geometry box

Tracing paper

Cutter

Prerequisite Knowledge

Straight angle

Exterior angle property of a triangle.

Theory

For straight line refer to Activity 11.

For exterior angle property of a triangle refer to Activity 12.

Procedure

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

Cut out a ΔABC from a glazed paper and paste it on the cardboard, (see Fig. 13.1)

ncert-class-9-maths-lab-manual-verify-exterior-angle-property-triangle-11

Now, produce the side BC of ΔABC to the point D. (see Fig. 13.2)

ncert-class-9-maths-lab-manual-verify-exterior-angle-property-triangle-12

Cut out the pair of angles, ∠A and ∠B from the glazed paper by using a tracing paper, (see Fig. 13.3).

ncert-class-9-maths-lab-manual-verify-exterior-angle-property-triangle-13

Now, arrange the cut out angles as shown in Fig. 13.4.

ncert-class-9-maths-lab-manual-verify-exterior-angle-property-triangle-14

Demonstration

From Fig. 13.4,

∠ACD is an exterior angle.

∠A and ∠B are its two interior opposite angles.

The two cut out angles, ∠A and ∠B together completely cover ∠ACD. So, ∠ACD = ∠A + ∠B.

Observation

Measure of ∠A = ……… , and ∠B = ……… ,

Sum of (∠A + ∠B) = ……… , and measure of ∠ACD = ……… ,

Therefore, ∠ACD = ∠A + ∠B.

Result

We have verified the exterior angle property of a triangle.

I hope this will help you

please mark it as brainlist answer

Answer 2

Answer:

Same as the first mark me as a brainliest answer