Solving Integral of csc^3(x)cot(x)

  • Thread starter ludi_srbin
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In summary, the conversation discusses different attempts at solving the integral of csc^3(x)cot(x). The suggested methods include using trig identities and substitution, with one suggestion using the derivative of csc(x) and the other using a more fundamental approach. Ultimately, all attempts resulted in the cancellation of terms.
  • #1
ludi_srbin
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Homework Statement



integral of csc^3(x)cot(x)

Homework Equations



I tried using trig identity 1+cot^2(x)=csc^2(x) but I got result where I canceled my indegrals.

The Attempt at a Solution



I tried to substitute the above mentioned indentity for csc^2 but I end up getting -cscx + intgr. cscxcot^3(x). I then substituted for cot^2 but then got to the point where I had -cscx + intgr. csc^(3)xcotx + cscx. At this point everything canceled out. I also tried substituting sin and cos in the original equation but that didn't get me anywhere neither.
 
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  • #2
Try splitting csc3(x)cot(x) into csc2(x)*(csc(x)cot(x)) does that help at all?
 
  • #3
write out [tex]\csc^3 (x), \cot(x)[/tex] in terms of [tex]\cos(x), \sin(x)[/tex] and use subsitution or do by inspection :smile:
 
  • #4
d_leet's suggestion is simpler (what is the derivative of csc(x)?) while mjsd's suggestion is more "fundamental" (you don't need to know the derivatiive of csc(x), only of cos(x)) but they both give the correct answer.
 

1. What is the formula for solving the integral of csc^3(x)cot(x)?

The formula for solving the integral of csc^3(x)cot(x) is ∫csc^3(x)cot(x)dx = -csc(x) + C, where C is the constant of integration.

2. Can the integral of csc^3(x)cot(x) be solved using u-substitution?

Yes, the integral of csc^3(x)cot(x) can be solved using u-substitution. Let u = csc(x), then du = -csc(x)cot(x)dx. Substituting this into the original integral gives ∫csc^3(x)cot(x)dx = ∫-u^2du = -u^3/3 + C = -csc^3(x)/3 + C.

3. What is the trigonometric identity used to solve the integral of csc^3(x)cot(x)?

The trigonometric identity used to solve the integral of csc^3(x)cot(x) is csc^2(x)cot(x) = csc(x).

4. Can the integral of csc^3(x)cot(x) be solved using integration by parts?

Yes, the integral of csc^3(x)cot(x) can be solved using integration by parts. Let u = csc^2(x) and dv = csc(x)cot(x)dx. Then du = -2csc(x)cot(x)dx and v = -csc(x). Substituting these into the integration by parts formula gives ∫csc^3(x)cot(x)dx = -csc^2(x) + 2∫csc(x)dx = -csc^2(x) + 2ln|csc(x) + cot(x)| + C.

5. Is there a shortcut method for solving the integral of csc^3(x)cot(x)?

Yes, there is a shortcut method for solving the integral of csc^3(x)cot(x). This integral can be rewritten as ∫csc^2(x)csc(x)cot(x)dx. Then using the trigonometric identity csc^2(x) = cot^2(x) + 1, the integral becomes ∫(cot^2(x) + 1)csc(x)cot(x)dx. Using u-substitution with u = cot(x), the integral simplifies to ∫u^2du = u^3/3 + C = cot^3(x)/3 + C.

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