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सिद्ध कीजिए - `2tan^(-1)((1)/(2))+tan^(-1)((1)/(7))=tan^(-1)((31)/(17)).` |
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Answer» L.H.S. `=2tan^(-1)((1)/(2))+tan^(-1)((1)/(7))` `=tan^(-1).((2xx(1)/(2))/(1-((1)/(2))^(2)))+tan^(-1)((1)/(7)),` `[because 2tan^(-1)x=tan^(-1)((2x)/(1-x^(2)))]` `=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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