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Babyslapmafro

  • 3 years ago

Could someone please verify that I solved the following integral correctly (click to see).

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  1. Babyslapmafro
    • 3 years ago
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    \[\int\limits_{}^{}\tan(x)\sec ^{3}(x)dx\] \[=\int\limits_{}^{}\tan(x)\sec(x)\sec ^{2}(x)dx\] \[=\int\limits_{}^{}\tan(x)\sec(x)u ^{2}\frac{ du }{ \sec(x)\tan(x) }\] \[=\int\limits_{}^{}u ^{2}du=\frac{ \sec ^{3}(x) }{ 3 }+C\]

  2. Babyslapmafro
    • 3 years ago
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    Idk if what I did was legal, but I got the right answer

  3. TuringTest
    • 3 years ago
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    Wes you solved it correctly, though you mixed your variables. You should never have u and x in the same expression.

  4. TuringTest
    • 3 years ago
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    Yes*

  5. Babyslapmafro
    • 3 years ago
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    I've seen u's and x's in the same expression many times, that's how x values are canceled and u's remain

  6. TuringTest
    • 3 years ago
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    I would have written\[\int\sec^3x\tan xdx=\]\[\int\sec^2x\sec x\tan xdx\]\[u=\sec x\implies du=\sec x\tan xdx\]and just subed in i'm not saying that what you did is totally wrong, I'm just saying it's a bad habit, and may confuse you later on. I do the trick you are referring to if I have only a constant that appears due to the u-sub, but with other variables it can get confusing. Still, right answer, nice job.

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