In a triangle ABC, frac{Delta^2}{a^2+b^2+c^2} | vedclass

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(B) We know that $r_1 = \frac{\Delta}{s-a}$, $r_2 = \frac{\Delta}{s-b}$, $r_3 = \frac{\Delta}{s-c}$, and $r = \frac{\Delta}{s}$.Substituting these int

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(B) We know that $r_1 = \frac{\Delta}{s-a}$, $r_2 = \frac{\Delta}{s-b}$, $r_3 = \frac{\Delta}{s-c}$, and $r = \frac{\Delta}{s}$.Substituting these into the expression:$\frac{\Delta^2}{a^2+b^2+c^2}\left(\frac{(s-a)^2}{\Delta^2}+\frac{(s-b)^2}{\Delta^2}+\frac{(s-c)^2}{\Delta^2}+\frac{s^2}{\Delta^2}\right)$$= \frac{1}{a^2+b^2+c^2}\left[(s-a)^2+(s-b)^2+(s-c)^2+s^2\right]$Using $s = \frac{a+b+c}{2}$, we have:$= \frac{1}{a^2+b^2+c^2}\left[\left(\frac{b+c-a}{2}\right)^2+\left(\frac{a+c-b}{2}\right)^2+\left(\frac{a+b-c}{2}\right)^2+\left(\frac{a+b+c}{2}\right)^2\right]$$= \frac{1}{a^2+b^2+c^2} \cdot \frac{1}{4} \left[(b+c-a)^2 + (a+c-b)^2 + (a+b-c)^2 + (a+b+c)^2\right]$Expanding the squares, the cross terms cancel out:$= \frac{1}{4(a^2+b^2+c^2)} \left[4(a^2+b^2+c^2)\right] = 1$.

List-$I$	List-$II$
$(A)$ $rr_2 = r_1r_3$	$(I)$ $\angle A = 90^{\circ}$
$(B)$ $r_1 + r_2 = r_3 - r$	$(II)$ $b^2 = c^2 + a^2$
$(C)$ $r_1 = r + 2R$	$(III)$ $\angle C = 90^{\circ}$
	$(IV)$ $\angle B = 120^{\circ}$

In a $\triangle ABC$, $\frac{\Delta^2}{a^2+b^2+c^2}\left(\frac{1}{r_1^2}+\frac{1}{r_2^2}+\frac{1}{r_3^2}+\frac{1}{r^2}\right) = $

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