So what can you do for this integral?

In summary, the integral being evaluated is \displaystyle\int {\frac{1}{secx+tanx} dx}, and the suggestion to solve it by taking the natural logarithm of the expression, ln|secx + tanx|, is incorrect. The correct approach is to write the tangent in terms of sine and cosine, and the secant as the reciprocal of the cosine.
  • #1
whatlifeforme
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0

Homework Statement


evaluate the integral.


Homework Equations



[itex]\displaystyle\int {\frac{1}{secx+tanx} dx}[/itex]

The Attempt at a Solution


can i just do ln|secx + tanx| ??
 
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  • #2
whatlifeforme said:

Homework Statement


evaluate the integral.

Homework Equations



[itex]\displaystyle\int {\frac{1}{secx+tanx} dx}[/itex]

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:
  • #3
whatlifeforme said:

Homework Statement


evaluate the integral.

Homework Equations



[itex]\displaystyle\int {\frac{1}{secx+tanx} dx}[/itex]

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 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.
 

Related to So what can you do for this integral?

What is an integral rational function?

An integral rational function is a type of mathematical function that can be written as a ratio of two polynomials, where the numerator and denominator are both polynomials with integer coefficients. It is also referred to as a rational expression.

What is the degree of an integral rational function?

The degree of an integral rational function is the highest power of the variable in the numerator or denominator of the function. It is determined by the highest degree term in the numerator, minus the highest degree term in the denominator. For example, the function f(x) = (3x^2 + x + 2) / (x^3 + 2x) has a degree of 2, since the highest degree term in the numerator is x^2 and the highest degree term in the denominator is x^3.

How do you simplify an integral rational function?

To simplify an integral rational function, you can factor both the numerator and denominator and cancel out any common factors. This will result in a simplified form of the function that has the same value as the original function. For example, the function f(x) = (x^2 + 4x + 4) / (x + 2) can be simplified to f(x) = x + 2 by factoring the numerator and canceling out the common factor of (x + 2).

What is the domain of an integral rational function?

The domain of an integral rational function is all the real numbers except for the values of x that would make the denominator equal to 0. This is because division by 0 is undefined. To find the domain, set the denominator equal to 0 and solve for x. Any values of x that make the denominator equal to 0 must be excluded from the domain.

How is an integral rational function graphed?

The graph of an integral rational function can be created by finding the x and y intercepts, identifying any vertical or horizontal asymptotes, and plotting a few other points to get a sense of the overall shape of the function. The graph will have a curve that may have breaks or holes at the x values where the denominator is equal to 0. It may also have asymptotes at these values or as x approaches positive or negative infinity.

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