Reduction formulas for integral of sin and cos

Click For Summary
SUMMARY

The discussion focuses on the integration of the function sin²(x)cos⁴(x) using reduction formulas. The user references a specific reduction formula for cos⁶(x), which is expressed as ∫ cos⁶(x) dx = (1/6)cos⁵(x)sin(x) + (5/6)∫ cos⁴(x) dx. The confusion arises when applying this formula to sin²(x)cos⁴(x), leading to the equation ∫ sin²(x)cos⁴(x) dx = (-1/6)cos⁵(x)sin(x) + (1/6)∫ cos⁴(x) dx. Clarification is sought on the transition of coefficients from 5/6 to 1/6 and the sign change to -1/6.

PREREQUISITES
  • Understanding of integral calculus, specifically integration by parts.
  • Familiarity with trigonometric identities and reduction formulas.
  • Knowledge of the properties of sine and cosine functions.
  • Experience with manipulating algebraic expressions in calculus.
NEXT STEPS
  • Study the derivation of reduction formulas for trigonometric integrals.
  • Learn how to apply integration by parts effectively in various scenarios.
  • Explore the relationship between sine and cosine functions in integrals.
  • Practice solving integrals involving products of sine and cosine functions.
USEFUL FOR

Students and educators in mathematics, particularly those focusing on calculus and integral techniques, as well as anyone looking to deepen their understanding of trigonometric integrals.

livvy07
Messages
6
Reaction score
0
Integrate sin2(x)cos4(x)dx using reduction formulas?
My book says integral sin2(x)cos4(x)dx= integral cos4(x)-integral cos6x dx
Now the reduction formula for n=6
for integral cos6(x)dx= (1/6)cos5(x)sinx+(5/6) integral cos4(x)dx

Here is the part I don't get: It then says :
sin2(x)cos4(x)dx
=(-1/6)cos5(x)sinx+(1/6) integral cos^4(x)dx

I don't get how the 5/6 becomes 1/6 or why 1/6 becomes -1/6 if that makes any sense? Any help would be great! I've been looking at it for awhile, but I am not seeing it for some reason.
 
Physics news on Phys.org
hi livvy07! :smile:

(have an integral: ∫ :wink:)

i don't understand that :confused:

∫ sin2(x)cos4(x) dx

= ∫ [sin(x)][sin(x)cos4(x)] dx

then integrate by parts (integrating the second bracket, and differentiating the first bracket)​
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 31 ·
2
Replies
31
Views
4K
  • · Replies 11 ·
Replies
11
Views
580
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K