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Prove-e-1-e-t-2-e-t-2-dt-1-1-e-2-e-the-base-of-natural-logarithm-




Question Number 218624 by Nicholas666 last updated on 13/Apr/25
      Prove; ∫^e _(1/e)  (t^2 /e^t^(2 )  ) dt ≤ 1− (1/e^(2  ) )     e−the base of natural logarithm
Prove;1eet2et2dt11e2ethebaseofnaturallogarithm
Answered by Nicholas666 last updated on 13/Apr/25
∫_(1/e) ^e  (t^2 /e^t^2  ) dt ≤1−(1/e^2 )  ⇒f′t=(d/dt)(t^2 e^(−t^2 ) )=2te^(−t^2 ) +t^2 (−2te^(−t^2 ) )=  2te^(−t^2 ) (1−t^2 )  ⇒f′(0.5)=2(0.5)e^(−(0.5)^2 ) =  e^(−0.25) (1−0.25)=0.75e^(−25) >0  ⇒f′(2)=2(2)e^(−2^2 ) (1−2^2 )=  4e^(−4) (1−4)=−12e^(−4) <0  ⇒f(1)=(1^2 /e^(12) )=(1/e)  ⇒∫_(1/e) ^e (t^2 /e^t^(2 )  )dt≤∫_(1/e) ^e (1/e)dt  ⇒∫_(1/e) ^e (1/e)dt=(1/e)∫_(1/e) ^e 1 dt=(1/e)[t]_(1/e) ^e  =  (1/e)(e−(1/e))=(e^(2−1) /e^2 )=1−(1/e^2 )  ⇒∫_(1/e) ^e (t^2 /e^t^2  )dt ≤1−(1/e^2 )     Q.E.D
1/eet2et2dt11e2ft=ddt(t2et2)=2tet2+t2(2tet2)=2tet2(1t2)f(0.5)=2(0.5)e(0.5)2=e0.25(10.25)=0.75e25>0f(2)=2(2)e22(122)=4e4(14)=12e4<0f(1)=12e12=1e1/eet2et2dt1/ee1edt1/ee1edt=1e1/ee1dt=1e[t]1/ee=1e(e1e)=e21e2=11e21/eet2et2dt11e2Q.E.D

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