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Evaluate the integral.\newline07π4tan(x7)dx \int_{0}^{\frac{7\pi}{4}} \tan \left( \frac{x}{7} \right) dx

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Q. Evaluate the integral.\newline07π4tan(x7)dx \int_{0}^{\frac{7\pi}{4}} \tan \left( \frac{x}{7} \right) dx
  1. Identify integral: Identify the integral to be solved.\newlineWe have the integral:\newline07π/4tan(x7)dx\int_{0}^{7\pi/4} \tan(\frac{x}{7}) \, dx
  2. Use substitution: Use a substitution to simplify the integral.\newlineLet u=x7u = \frac{x}{7}, which implies that x=7ux = 7u. Then, we need to find dxdx in terms of dudu.\newlinedx=7dudx = 7 du
  3. Change limits: Change the limits of integration according to the substitution.\newlineWhen x=0x = 0, u=07=0u = \frac{0}{7} = 0.\newlineWhen x=7π4x = \frac{7\pi}{4}, u=(7π/4)7=π4u = \frac{(7\pi/4)}{7} = \frac{\pi}{4}.\newlineSo the new limits of integration are from u=0u = 0 to u=π4u = \frac{\pi}{4}.
  4. Rewrite in terms of uu: Rewrite the integral in terms of uu.0π4tan(u)7du\int_{0}^{\frac{\pi}{4}} \tan(u) \cdot 7 \, du
  5. Factor out constant: Factor out the constant from the integral. 7×0π4tan(u)du7 \times \int_{0}^{\frac{\pi}{4}} \tan(u) \, du
  6. Integrate tan(u)\tan(u): Integrate tan(u)\tan(u) with respect to uu. The integral of tan(u)\tan(u) is lncos(u)-\ln|\cos(u)|. So we have: 7×[lncos(u)]7 \times [-\ln|\cos(u)|] evaluated from 00 to π4\frac{\pi}{4}
  7. Evaluate at limits: Evaluate the antiderivative at the upper and lower limits.\newline7×[lncos(π/4)+lncos(0)]7 \times [-\ln|\cos(\pi/4)| + \ln|\cos(0)|]\newline= 7×[ln(2/2)+ln(1)]7 \times [-\ln(\sqrt{2}/2) + \ln(1)]\newline= 7×[0(ln(2/2))]7 \times [0 - (-\ln(\sqrt{2}/2))]\newline= 7×ln(2/2)7 \times \ln(\sqrt{2}/2)
  8. Simplify expression: Simplify the expression.\newline7ln(2/2)=7ln(1/2)=7ln(2(1/2))=7(1/2)ln(2)7 \cdot \ln(\sqrt{2}/2) = 7 \cdot \ln(1/\sqrt{2}) = 7 \cdot \ln(2^{(-1/2)}) = 7 \cdot (-1/2) \cdot \ln(2)\newline=72ln(2)= -\frac{7}{2} \cdot \ln(2)

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