Definite Integral of Trig Function

  • Thread starter Jimbo57
  • Start date
  • #1
96
0

Homework Statement


∫sin2xcosx x=0,pi/4


Homework Equations





The Attempt at a Solution


By double angle magic:
∫sin2xcosx=
∫2sinxcos^2x
u=cosx
du=-sinxdx
-2∫u^2
-2(u^3)/3
-2cos^3x/3
= -1/(3√2) for x=pi/4

How does that look folks?
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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Hi Jimbo57! :smile:

(have a pi: π and try using the X2 button just above the Reply box :wink:)

Fine down to …
-2cos^3x/3
= -1/(3√2) for x=pi/4

… what about for x = 0 ? :wink:
 
  • #3
96
0
Hi Jimbo57! :smile:

(have a pi: π and try using the X2 button just above the Reply box :wink:)

Fine down to …


… what about for x = 0 ? :wink:

Lol woops, I'm used to ignoring the 0 with non trig integrals.

New answer:

(-1+2√2)/3√2

Thanks for the help Tiny-Tim! (and the pi)
 

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