How to integrate sinx/(1+sinx)

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In summary, the conversation discusses a problem where the solution involves multiplying the top and bottom by a certain quantity and considering the identity 1-\sin^2x=\cos^2x. The conversation also mentions using the Pythagorean Conjugate to solve the problem.
  • #1
mathnoobie
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Homework Statement


As stated in the title.


Homework Equations


No equations


The Attempt at a Solution


Honestly, I'm stuck. I have no idea where to go. My only thought is to multiply the top and bottom by sinx but where would that get me?
 
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  • #2
I agree you should multiply the denominator and numerator by some quantity. As a hint, it might be useful to consider that [itex]1-\sin^2x=\cos^2 x[/itex].
 
  • #3
16180339887 said:
I agree you should multiply the denominator and numerator by some quantity. As a hint, it might be useful to consider that [itex]1-\sin^2x=\cos^2 x[/itex].

Yes, I did that, and am confused where to go from there.
 
  • #4
Multiple the top and bottom by sin2x
 
  • #5
Solved it. Multiplied the top and bottom by the Pythagorean Conjugate.
 

1. What is the general method for integrating sinx/(1+sinx)?

The general method for integrating sinx/(1+sinx) is to use the substitution method. Let u = 1+sinx and du = cosx dx. Then, the integral becomes ∫(1/u) du, which can be easily integrated to get ln|u| + C. Substituting back in for u, the final answer is ln|1+sinx| + C.

2. Can the integral be solved using other methods?

Yes, the integral can also be solved using the trigonometric identity cos^2x + sin^2x = 1. Rearranging this to solve for sinx, we get sinx = √(1-cos^2x). Substituting this into the integral and using the substitution method, we get ∫√(1-cos^2x) dx, which can be solved using the power rule to get (1/2)(x-1/4sin2x) + C.

3. Are there any special cases to consider when integrating sinx/(1+sinx)?

Yes, when the integral is in the form ∫sinx/(1+cosx) dx, it can be easily solved by using the substitution method with u = 1+cosx and du = -sinx dx. However, if the integral is in the form ∫sinx/(1-sinx) dx, it cannot be solved using the substitution method and a different approach must be taken.

4. Is there a way to simplify the integral before integrating?

Yes, the integral can be simplified by using the trigonometric identity sinx/(1+sinx) = 1-1/(1+sinx). This simplifies the integral to ∫(1-1/u) du, which can be easily integrated to get u-ln|u| + C. Substituting back in for u, the final answer is (1+sinx)ln|1+sinx| - sinx + C.

5. Can the integral be solved using numerical methods?

Yes, the integral can be solved using numerical methods such as the trapezoidal rule or Simpson's rule. These methods involve approximating the integral using smaller subintervals and calculating the area under the curve. While these methods may not give an exact solution, they can provide a close approximation for the integral.

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