Explanation: 
Another Explanation (5):
সমাধান: 🤔
ধরি, \( tan(5x) = u \)
তাহলে, \( 5sec^2(5x) dx = du \)
সুতরাং, \( sec^2(5x) dx = \frac{1}{5} du \)
এখন,
\( \int tan^3(5x) sec^2(5x) dx = \int u^3 \frac{1}{5} du \)
\( = \frac{1}{5} \int u^3 du \)
\( = \frac{1}{5} \cdot \frac{u^4}{4} + C \)
\( = \frac{1}{20} u^4 + C \)
\( = \frac{1}{20} tan^4(5x) + C \) ✅
অতএব, \( \int tan^3(5x) sec^2(5x) dx = \frac{1}{20} tan^4(5x) + C \) 🥳