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Sum

In ∆LMN, l = 5, m = 13, n = 12 then complete the activity to show that whether the given triangle is right angled triangle or not.

*(l, m, n are opposite sides of ∠L, ∠M, ∠N respectively)

Activity: In ∆LMN, l = 5, m = 13, n = `square`

∴ l^{2} = `square`, m^{2} = 169, n^{2} = 144.

∴ l^{2} + n^{2} = 25 + 144 = `square`

∴ `square` + l^{2} = m^{2}

∴By Converse of Pythagoras theorem, ∆LMN is right angled triangle.

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#### Solution

In ∆LMN,

l = 5, m = 13, n = **12**

∴ l^{2} = **25**, m^{2} = 169, n^{2} = 144.

∴ l^{2} + n^{2} = 25 + 144 = **169**

∴ **n ^{2}** + l

^{2}= m

^{2}

∴By Converse of Pythagoras theorem, ∆LMN is right angled triangle.

Concept: Converse of Pythagoras Theorem

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