## nijhu 3 years ago |dw:1349516917936:dw|

1. hartnn

draw it out again

2. nijhu

ok

3. nijhu

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4. hartnn

u need to evaluate that ? its w.r.t du , right ? which topic does this question belong ?

5. nijhu

i need to solve this by using convollution theorem

6. nijhu

it is a laplace transform

7. hartnn

Laplace or Fourier ? F = Fourier generally

8. nijhu

we r following th e book laplace transform by spiegel

9. nijhu

and the topic is alpplications to differential equations by using inverse laplace

10. nijhu

anyone got my answr

11. nijhu

?

12. hartnn

$$\large \frac{s}{5}\frac{5}{(s^2+9)(s^2+4)}= \quad \frac{s}{5}\frac{(s^2+9)-(s^2+4)}{(s^2+9)(s^2+4)}$$ now just separate denominator. got it ?

13. nijhu

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14. hartnn

don't include s. lets just do partial fraction for 1/(s^2+4)(s^2+9) after that we multiply s to both terms

15. hartnn

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16. nijhu

hmmm then?

17. hartnn

what vales of A and b u got ?

18. nijhu

A=1/85 and B=1/25

19. hartnn

how ! 1= A (s^2+4) + B (s^2+9) put s^2 = -9 1= A (-9+4) 1= A (-5) A = -1/5 got this ?

20. hartnn

similarly find B

21. nijhu

B=1/5

22. hartnn

thats correct. so now u got where that 1/5 came from ?

23. nijhu

lol....

24. nijhu

got it

25. nijhu

26. nijhu

thanks a lot man!

27. hartnn

welcome ^_^

28. nijhu

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29. hartnn

thats just separation of variables, which step did u not get ?

30. nijhu

(s^2+4)dy/ds+sy=0....how did the minus sign cancel out?

31. nijhu

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32. nijhu

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33. hartnn

u r rite, even i don't see, how they got that + maybe printing mistake in book.....

34. nijhu

my sir showed us a similar problem where the condition Y(0)=1,Y(pie)=0 and Y'(0)=c