1.

In a ` A B C ,`, if C is a right angle, then `tan^(-1)(a/(b+c))+tan^(-1)(b/(c+a))=``pi/3`(b) `pi/4`(c) `(5pi)/2`(d) `pi/6`

Answer» `tan^-1 x + tan^-1 y = tan^-1 ((x+y)/(1-xy))`
so, `tan^-1 (a/(b+c)) + tan^-1(b/(a+c))`
`tan^-1((a/(b+c) + b/(a+c))/(1- (ab)/((a+c)(b+c))))`
`= tan^-1[ (a^2 + ac + b^2 + bc)/(ab + bc + ac + c^2 - ab)]`
`= tan^-1[(a^2+ b^2 + ac+bc)/(bc + ac+c^2)]`
so, `/_ c= pi/2`
`cos c = (a^2 + b^2 - c^2)/(2ab)=0`
`a^2 + b^2 = c^2`
`tan^-1 [ (bc+ac+c^2)/(bc + ac+c^2)]`
`= tan^-1 1 = pi/4`
Answer


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