So what can you do for this integral?

whatlifeforme
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Homework Statement


evaluate the integral.


Homework Equations



\displaystyle\int {\frac{1}{secx+tanx} dx}

The Attempt at a Solution


can i just do ln|secx + tanx| ??
 
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whatlifeforme said:

Homework Statement


evaluate the integral.

Homework Equations



\displaystyle\int {\frac{1}{secx+tanx} dx}

The Attempt at a Solution


can i just do ln|secx + tanx| ??
Probably not.

What's the derivative of ln|secx + tanx| ?

Added in Edit:

Write the tangent in terms of sine & cosine and the secant as the reciprocal of the cosine.
 
Last edited:
whatlifeforme said:

Homework Statement


evaluate the integral.

Homework Equations



\displaystyle\int {\frac{1}{secx+tanx} dx}

The Attempt at a Solution


can i just do ln|secx + tanx| ??

No. You're making the same mistake you made in this thread: https://www.physicsforums.com/showthread.php?t=678488.

It is NOT TRUE[/color] that
$$ \int \frac{dx}{f(x)} = ln|f(x)| + C$$

The above is true only if f(x) = x, which is certainly not the case here.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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