Gujarat BoardEnglish MediumSTD 12 ScienceMathsIntegrals3 Marks
Question
Find the integral of the function tan4 x
✓
Answer
tan4 x = tan2 x.tan2 x = (sec2 x - 1) tan2 x = sec2 x tan2 x - tan2 x = sec2 x tan2 x - (sec2 x - 1) = sec2 x tan2 x - sec2 x + 1 Now, $\int \tan ^{4} x d x=\int \sec ^{2} x \tan ^{2} x d x-\int \sec ^{2} x d x+\int 1 d x$ $= \int \sec ^{2} x \tan ^{2} x d x-\tan x+x+C$ Now, let tanx = t $\Rightarrow$ sec2x dx = dt $\Rightarrow \int \sec ^{2} x \tan ^{2} x d x=\int t^{2} d t=\frac{t^{3}}{3}=\frac{\tan ^{3} x}{3}$ $\Rightarrow \int \tan ^{4} x d x=\frac{1}{3} \tan ^{3} x-\tan x+x+C$
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