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Evaluate the integral.\newline6sec2(3t)7+2tan(3t)dt\int\frac{6\sec^{2}(3t)}{7+2\tan(3t)}\,dt

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Q. Evaluate the integral.\newline6sec2(3t)7+2tan(3t)dt\int\frac{6\sec^{2}(3t)}{7+2\tan(3t)}\,dt
  1. Identify Substitution: Let's start by identifying a substitution that can simplify the integral. We notice that the derivative of tan(3t)\tan(3t) is sec2(3t)\sec^2(3t) multiplied by the constant 33. This suggests that a substitution involving tan(3t)\tan(3t) might be useful. Let's set u=tan(3t)u = \tan(3t), which means dudt=3sec2(3t)\frac{du}{dt} = 3\sec^2(3t).
  2. Express in terms of uu: Now we need to express the integral in terms of uu. We have du=3sec2(3t)dtdu = 3\sec^2(3t)dt, so dt=du3sec2(3t)dt = \frac{du}{3\sec^2(3t)}. We also need to express the sec2(3t)\sec^2(3t) term in the numerator in terms of uu. Since sec2(3t)=1+tan2(3t)\sec^2(3t) = 1 + \tan^2(3t), we can write sec2(3t)\sec^2(3t) as 1+u21 + u^2.
  3. Substitute uu and dtdt: Substituting uu and dtdt into the integral, we get:\newline6sec2(3t)7+2tan(3t)dt=6(1+u2)7+2u(du3(1+u2))\int\frac{6\sec^2(3t)}{7+2\tan(3t)}\,dt = \int\frac{6(1+u^2)}{7+2u} \cdot \left(\frac{du}{3(1+u^2)}\right)\newlineSimplifying this, we get:\newline67+2u(du3)=27+2udu\int\frac{6}{7+2u} \cdot \left(\frac{du}{3}\right) = \int\frac{2}{7+2u} \,du
  4. Integrate rational function: The integral 27+2udu\int \frac{2}{7+2u} \, du is a simple rational function, and we can integrate it directly. The antiderivative of 1a+bu\frac{1}{a+bu} with respect to uu is (1b)lna+bu(\frac{1}{b})\ln|a+bu|, so the antiderivative of 27+2u\frac{2}{7+2u} with respect to uu is (12)ln7+2u(\frac{1}{2})\ln|7+2u|.
  5. Substitute back to t: Now we substitute back the original variable t into our antiderivative. Since u=tan(3t)u = \tan(3t), we have:\newline(1/2)ln7+2u=(1/2)ln7+2tan(3t)+C(1/2)\ln|7+2u| = (1/2)\ln|7+2\tan(3t)| + C, where CC is the constant of integration.
  6. Final Antiderivative: We have found the antiderivative, so the integral of 6sec2(3t)7+2tan(3t)\frac{6\sec^2(3t)}{7+2\tan(3t)} with respect to tt is: \frac{\(1\)}{\(2\)}\ln|\(7+22\tan(33t)| + C