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Getting Natural With Pi (Posted on 2007-11-27) Difficulty: 3 of 5
Determine the value of the constant y, whenever:
       y
     (ex - 1)-0.5 dx = pi/6 
      ln(4/3)

where ln x denotes the natural logarithm of x.

  Submitted by K Sengupta    
Rating: 3.0000 (2 votes)
Solution: (Hide)
Let √(ex -1) = q

Then,

  y
   ∫ (ex -1)-0.5 dx
ln(4/3)

= 2*I, where:

I =

√(e^y - 1)
    ∫  (1 + q^2)-1 dq
1/√3

= arc tan √(e^y -1) – pi/6

Accordingly, 2(arc tan √(e^y -1) – pi/6) = pi/6, giving:

arc tan √(e^y -1) = pi/4, so that:

e^y - 1 = 1, giving:

e^y = 2, so that: y = ln(2)

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re(4): True, there is only one solution.Kurious2007-11-29 07:07:16
re(3): There are two solutionsCharlie2007-11-28 09:23:19
re(2): There are two solutionsKurious2007-11-28 07:28:10
re: There are two solutionsCharlie2007-11-27 21:53:38
SolutionThere are two solutionsKurious2007-11-27 18:54:23
SolutionSwitch to other integral!Chesca Ciprian2007-11-27 14:34:19
Solutionanalytical solutionDaniel2007-11-27 13:51:46
Solutionnumerical solution -- spoilerCharlie2007-11-27 10:43:27
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