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`int(1)/((1tan x))dx` का मान ज्ञात कीजिए।

Answer» माना `I = int (1)/((1+tanx)) dx = int(1)/((1+(sinx)/(cosx))) dx`
` = int (1)/(((cosx + sinx)/(cosx)))dx = int(cosx)/((cosx + sinx))dx`
` =int ((cos x + sinx)+(cosx-sinx))/(2(cos x+sinx))dx`
` = (1)/(2)int((cosx + sinx))/((cos x+sinx))dx +(1)/(2)int((cosx - sinx))/((cos x + sinx))dx`
` = (1)/(2)int dx + (1)/(2)int((cos x - sin))/((cos x + sinx))dx`
यदि `(cos x + sinx) = t`
व `(cos x - sinx) dx = dt`
अब `I = (1)/(2) int dx + (1)/(2) int(1)/(t) dt`
` =(1)/(2) x +(1)/(2)log |t| +c = (1)/(2) x +(1)/(2)log |cos x+ sin x|+c`


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