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AravindG

find local maxima and local minima for the function f(x)=sin x-cos x 0<x<2

  • one year ago
  • one year ago

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  1. AravindG
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    @hartnn

    • one year ago
  2. uzumakhi
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    for this you have to find f'(x)

    • one year ago
  3. AravindG
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    ok ....cos x + sin x then?

    • one year ago
  4. uzumakhi
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    and then take f'(x)=0

    • one year ago
  5. AravindG
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    sin x+cos x=0

    • one year ago
  6. AravindG
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    sinx=-cos x

    • one year ago
  7. AravindG
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    nw what ?

    • one year ago
  8. uzumakhi
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    cos x + sin x = 0 cos x = -sinx

    • one year ago
  9. AravindG
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    k then ?

    • one year ago
  10. AravindG
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    why u delete that?

    • one year ago
  11. uzumakhi
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    find the value of x

    • one year ago
  12. AravindG
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    x=-pi/4 isnt it?

    • one year ago
  13. uzumakhi
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    no we have to take the value from 0 to 2

    • one year ago
  14. AravindG
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    then hw ??

    • one year ago
  15. uzumakhi
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    take x = 135 degrees

    • one year ago
  16. uzumakhi
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    convert it to radians

    • one year ago
  17. AravindG
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    2.355

    • one year ago
  18. AravindG
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    x=3pi/4

    • one year ago
  19. hartnn
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    if x is between 0 to 2pi, then x= 3pi/4 is correct.

    • one year ago
  20. AravindG
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    k then hw we find local maxima and local minima ?

    • one year ago
  21. hartnn
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    local only means 'in that interval' , here 0 to 2pi

    • one year ago
  22. AravindG
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    so what are maxima and minima here ?

    • one year ago
  23. hartnn
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    so here u'll have only one value , at x=3pi/4 find f(x) when x=3pi/4

    • one year ago
  24. AravindG
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    also at x=7pi/4 we have only one value so f'(X)= ives 2 values for x isnt it?

    • one year ago
  25. AravindG
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    f'(X)=0 gives 2 values for x isnt it?

    • one year ago
  26. hartnn
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    oh yes! i missed that. now its even simpler..... find the second derivate, what u get ?

    • one year ago
  27. AravindG
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    -sinx +cos x

    • one year ago
  28. AravindG
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    whats the use of taking second derivative ?

    • one year ago
  29. hartnn
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    to know which point is max. or min. , u know how ?

    • one year ago
  30. AravindG
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    nop

    • one year ago
  31. AravindG
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    is it by substituting 3pi/4 and 7pi/4 in f''(X) and getting the sign to tell which is maxima and minima?

    • one year ago
  32. AravindG
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    k gt it !!!

    • one year ago
  33. hartnn
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    yes, if f''(x) > 0 , then max or min ?

    • one year ago
  34. hartnn
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    ok, good :)

    • one year ago
  35. AravindG
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    3pi/4 is max other is minima !!

    • one year ago
  36. AravindG
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    can u check up the answer for the next qn also ?

    • one year ago
  37. hartnn
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    sure ...

    • one year ago
  38. AravindG
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    i will post separately

    • one year ago
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