Page 51 - Mathematics Class - IX

6. Compare the cut out of the angle with remaining angles (Fig. (d)).

A A

B C B C
A A

Fig. (d)

OBSERVATIONS

Length of side AB = .......................

Length of side BC = .......................
Length of side CA = .......................

Measure of the angle opposite to longest side = .......................
Measure of the other two angles = ...................... and .......................

The angle opposite to the ...................... side is ...................... than the other two angles.

INFERENCE

We came to know that
∠A > ∠B and ∠A > ∠C

So, we get

BC > AC, since ∠A > ∠B
Also, BC > AB, since ∠A > ∠C

Thus, we observe that the angle belongs to longer side is greater than the angles opposite to the other sides.

EXTENDED TASK

1. Verify experimentally the relation between unequal sides of a triangle and the angles opposite to them.

2. Verify that the difference of any two sides of a triangle is always less than the third side.

APPLICATION

The result can be used in different geometrical problems.

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