Tuesday, March 4, 2014

Calculate the definite integral of f2(x), if fa(x)=1/(|x-a|+3)? limits of integration are x=0 and x=3

Since fa(x)=1/(|x-a|+3), then f2(x) =
1/(|x-2|+3).


We'll have to solve the definite integral of
f2(x) = 1/(|x-2|+3)


Int
dx/(|x-2|+3)


We'll discuss the absolute
value:


|x-2| = x-2, for
x>2


|x-2| = -x+2, for
x<2


Since the limits of integration are x = 0 to x =
3, we'll split the interval in 2:


x = 0 to x = 2 and x = 2
to x = 3, since the function has different expressions over the ranges [0,2] and
[2,3].


Int dx/(|x-2|+3) = Int dx/(5-x) + Int
dx/(x+1)


Int dx/(5-x) = F(2) –
F(0)


Int dx/(x+1) = F(3) –
F(2)


But Int dx/(5-x) =
-ln|x-5|


F(2) – F(0) = -ln|2-5| + ln|0-5| = -ln3 + ln 5 =
ln (5/3)


Int dx/(x+1) =
ln|x+1|


F(3) – F(2) = ln|3+1| - ln|2+1| = ln 4-ln3 = ln 
(4/3)


Int dx/(|x-2|+3) = ln (5/3) + ln  (4/3) = ln
20/9


The definite integral of the function
f2(x) = 1/(|x-2|+3) is Int dx/(|x-2|+3) = ln
20/9.

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