If $I_n=\int_0^{\frac{\pi}{4}} \tan ^n \theta d \theta$, then $I_{12}+I_{10}=$

If $I_n=\int_0^{\frac{\pi}{4}} \tan ^n \theta d \theta$, then $I_{12}+I_{10}=$
  1. $\frac {1}{8}$
  2. $\frac {1}{12}$
  3. $\frac {1}{11}$
  4. $\frac {1}{10}$

Solution

$\begin{aligned} & \int_0^{\frac{\pi}{4}}\left(\tan ^{\mathrm{n}} x+\tan ^{\mathrm{n}-2} x\right) \mathrm{d} x=\frac{1}{\mathrm{n}-1} \\ & \therefore \quad \mathrm{I}_{12}+\mathrm{I}_{10}=\int_0^{\frac{\pi}{4}}\left(\tan ^{12} \theta+\tan ^{10} \theta\right) \mathrm{d} \theta \\ &=\frac{1}{12-1} \\ &=\frac{1}{11}\end{aligned}$

Asked in: MHT CET 2023 (14 May Shift 2)

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