Curve .Find the area under the curve 1/x .

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sciencesolve | Teacher | (Level 3) Educator Emeritus

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You need to evaluate the integral of rational function f(x)=1/x such that:

int (1/x)dx = ln|x| + c

The problem does not provide the information concerning the boundary limits of the area to be evaluated.

Supposing that the upper limit is e and the lower limit is 1, you should evaluate the area such that:

int_1^e (1/x)dx = ln e - ln 1

Since ln e=1 and ln 1=0, then int_1^e (1/x)dx = 1, hence, the areaof the region bounded by the curve 1/x,x axis and boundary limits 1 and e is of 1 square unit.

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giorgiana1976 | College Teacher | (Level 3) Valedictorian

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The area under the curve 1/x, is the definite integral of f(x) minus INtegral of another curve or line and between the limits x = a and x = b.

Since there are not specified the limits x = a and x = b, also it is not specified the other curve or line, we'll calculate the indefinite integral of 1/x and not the area under the curve.

The indefinite integral of f(x) = 1/x is:

Int f(x) = Int dx/x

Int dx/x = ln x + C

C - family of constants.

To understand the family of constants C, we'll consider the result of the indefinite integral as the function f(x).

f(x) = ln x + C

We'll differentiate f(x):

f'(x) = (ln x + C)'

f'(x) = 1/x + 0

Since C is a constant, the derivative of a constant is cancelling.

So, C could be any constant, for differentiating f(x), the constant will be zero.

Now, we'll calculate the area located between the curve 1/x, x axis, x=a and x=b:

Integral [f(x) - ox]dx, x = a to x = b

We'll apply Leibniz-Newton formula:

Int f(x) dx = F(b) - F(a)

Int dx/x = ln b - ln a

Since the logarithms have matching bases, we'll transform the difference into a product:

Int dx/x = ln |b/a|

The area located between the curve 1/x, x axis, x=a and x=b is:

Int dx/x = ln |b/a|

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