1.

In `DeltaABC` , the value of `(cotA/2cotB/2-1)/(cotA/2cotB/2)` isA. `(a)/(a+b+c)`B. `(2c)/(a+b+c)`C. `(2a)/(a+b+c)`D. `(2b)/(a+b+c)`

Answer» Correct Answer - B
`(cot.(A)/(2) cot.(B)/(2)-1)/(cot.(A)/(2)cot.(B)/(2))`
` = - 1 tan.(A)/(2) tan (B)/(2)`
`=1 - sqrt(((s-b)(s-c))/(s(s-a))) sqrt(((s-a)(s-c))/(s(s-b)))`
`=1- (S-C)/(S) =(C)/(S)`
` = (2C)/(a+b+c)`


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