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Question Number 22714 by selestian last updated on 22/Oct/17

Answered by ajfour last updated on 22/Oct/17

$$\lambda =a+b+c$$$$letl=b\cos {}^2\left(\frac{C}{2}\right)+c\cos {}^2\left(\frac{B}{2}\right)$$$$\Rightarrow 2l=b(1+\cos C)+c(1+\cos B)$$$$\Rightarrow 2l=b+c+(b\cos C+c\cos B)$$$$or2l=b+c+a$$$$\Rightarrow l==\frac{(a+b+c)}{2}=\frac{\lambda }{2}.$$

Commented by selestian last updated on 22/Oct/17

$$thAnkyousomuchsir...$$

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