We'll use the following formula to calculate the length of
the arc of the graph of
parabola:
b
`int`
sqrt[1+|f'(x)|^2]dx
a
Therefore,
we need to determine the derivative of the function, using the quotient
rule:
f'(x) =
-8(x-2)/16(x-2)^4
f'(x) =
-1/2(x-2)^3
The arc length of of f from x = -2 to x = 4
is:
4
4
`int` sqrt[1 + 1/4(x-2)^6]dx = `int` {sqrt[(x-2)^6 +
1]}dx/2(x-2)^3
-2
-2
To calculate the definite integral above, we'll use the
following formula:
`int` rdt/t = r - a*ln|(a+r)/t|, where r
= sqrt (t^2 + a^2)
If t = (x-2)^3 and a = 1, we'll
have:
`int` {sqrt[(x-2)^6 + 1]}dx/2(x-2)^3 =
(1/2)*{sqrt[(x-2)^6 + 1] - ln|{1+sqrt[(x-2)^6 + 1]}/(x-2)^3|} +
C
To evaluate the definite integral, we'll use Leibniz
Newton formula:
4
`int`
{sqrt[(x-2)^6 + 1]}dx/2(x-2)^3= F(4) -
F(2)
-2
F(4) =
(1/2)*{sqrt[(2)^6 + 1] - ln|{1+sqrt[(2)^6 +
1]}/(2)^3|}
F(4) = (1/2)*[sqrt65 -
ln|(1+sqrt65)/8|]
F(4) =
(1/2)*(8.062-0.123)
F(4) =
3.969
F(-2) = (1/2)*{sqrt[(-4)^6 + 1] - ln|{1+sqrt[(-4)^6
+ 1]}/(-4)^3|}
F(-2) =
32.003
4
`int` {sqrt[(x-2)^6 +
1]}dx/2(x-2)^3=28.034
-2
The
arc length of of y = 1/4(x-2)^2 + 1, from x = -2 to x = 4 is of
28.034.
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