1.

`2tan^(-1)""(1)/(2)+tan^(-1)""(1)/(7)=tan^(-1)""(31)/(17)`

Answer» `L.H.S.=2tan^(-1)""(1)/(2)+tan^(-1)""(1)/(7)`
`=tan^(-1)((2xx(1)/(2))/(1-(1)/(4)))+tan^(-1)""(1)/(7)`
`=tan^(-1)""(4)/(3)+tan^(-1)""(1)/(7)`
`tan^(-1)""((4)/(3)+(1)/(7))/(1-(4)/(3)xx(1)/(7))=tan^(-1)""((28+3)/(21))/((21-4)/21)`
`tan^(-1)""(31)/(17)=R.H.S.`


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