Integral of sin(1-x)sinx

  • #1

Homework Statement



integral of sin(1-x)sinx dx

Homework Equations





The Attempt at a Solution



so i did by parts once and got -sinxcos(1-x) - integral of -cos(1-x)cosx dx

then i did by parts again and got -sinxcos(1-x) + cosxsin(1-x) - integral of -sin(1-x)sinx dx

if you take out the negative on the last integral you end up where you started? any one know where i messed up?
 

Answers and Replies

  • #2
Instead of parts, you could try using a double angle formula on sin(1-x).
 
  • #3
oh i think i see it i forgot to divide by the -1 each time i took the integral in the by parts
 
  • #4
nevermind i still did not get the right answer how do i use double angle on sin(1-x_ i thought it had to be in the form sin2x?
 
  • #5
fzero
Science Advisor
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Not quite the double angle formula, but rather the trig identity for sin of a sum.
 
  • #6
i got it now thx
 

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