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Mathematics

Lengths of sides of triangle are given below. Determine which of them are right triangles. In case of a right triangle, write the length of its hypotenuse:

(i) 3 cm, 8 cm, 6 cm

(ii) 13 cm, 12 cm, 5 cm

(iii) 1.4 cm, 4.8 cm, 5 cm

Pythagoras Theorem

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Answer

Choose the greatest length. Check whether the square of greatest length is equal to the sum of squares of other two lengths.

(i) Here greatest length is 8 cm and other lengths are 3 cm, 6 cm.

Note that 82 = 64 and 32 + 62 = 9 + 36 = 45.

Note that, 64 ≠ 45.

Hence, the triangle with given lengths of sides is not a right triangle.

(ii) Here greatest length is 13 cm and other lengths are 5 cm, 12 cm.

Note that 132 = 169 and 52 + 122 = 25 + 144 = 169.

Thus, 132 = 52 + 122.

Hence, the triangle with given lengths of sides is a right triangle and length of hypotenuse is 13 cm.

(iii) Here greatest length is 5 cm and other lengths are 1.4 cm, 4.8 cm.

Note that 52 = 25 and (4.8)2 + (1.4)2 = 23.04 + 1.96 = 25.

Thus, 52 = (4.8)2 + (1.4)2.

Hence, the triangle with given lengths of sides is a right triangle and length of hypotenuse is 5 cm.

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