The problem asks us to find the equation of a tangent line $l$ drawn from the point $(0, 1)$ to the curve $C: y = \log(2x)$. Then, we need to find the area of the region enclosed by the curve $C$, the tangent line $l$, the $x$-axis, and the $y$-axis.

AnalysisCalculusTangent LinesIntegrationDefinite IntegralsLogarithmic Functions
2025/5/3

1. Problem Description

The problem asks us to find the equation of a tangent line ll drawn from the point (0,1)(0, 1) to the curve C:y=log(2x)C: y = \log(2x). Then, we need to find the area of the region enclosed by the curve CC, the tangent line ll, the xx-axis, and the yy-axis.

2. Solution Steps

(1) Find the equation of the tangent line ll.
Let the point of tangency be (t,log(2t))(t, \log(2t)).
The derivative of y=log(2x)y = \log(2x) is y=1xy' = \frac{1}{x}.
So, the slope of the tangent line at x=tx = t is 1t\frac{1}{t}.
The equation of the tangent line is
ylog(2t)=1t(xt)y - \log(2t) = \frac{1}{t}(x - t).
Since the tangent line passes through (0,1)(0, 1), we can substitute x=0x = 0 and y=1y = 1 into the equation:
1log(2t)=1t(0t)=11 - \log(2t) = \frac{1}{t}(0 - t) = -1
log(2t)=2\log(2t) = 2
2t=e22t = e^2
t=e22t = \frac{e^2}{2}
Then, the slope of the tangent line is 1t=2e2\frac{1}{t} = \frac{2}{e^2}.
The point of tangency is (e22,log(e2))=(e22,2)(\frac{e^2}{2}, \log(e^2)) = (\frac{e^2}{2}, 2).
The equation of the tangent line is:
y2=2e2(xe22)y - 2 = \frac{2}{e^2}(x - \frac{e^2}{2})
y=2e2x1+2y = \frac{2}{e^2}x - 1 + 2
y=2e2x+1y = \frac{2}{e^2}x + 1
Therefore, the first box should be 2, and the second box should be

1. (2) Find the area of the region enclosed by the curve $C$, the tangent line $l$, the $x$-axis, and the $y$-axis.

The intersection of the tangent line and the xx-axis is when y=0y = 0.
0=2e2x+10 = \frac{2}{e^2}x + 1
x=e22x = -\frac{e^2}{2}, which is not relevant as xx must be positive.
The curve C:y=log(2x)C: y = \log(2x) intersects the xx-axis when y=0y = 0.
0=log(2x)0 = \log(2x)
2x=12x = 1
x=12x = \frac{1}{2}.
The intersection of tangent ll with yy axis is when x=0x = 0, so y=1y=1. The area is bounded by curve y=log(2x)y = \log(2x), x=1/2x = 1/2, and y=2e2x+1y = \frac{2}{e^2} x+ 1.
Area = 01/2(2e2x+1)dx1/2e2/2(log(2x)dx0=1/2e2/2log(2x)dx\int_{0}^{1/2} (\frac{2}{e^2}x + 1)dx - \int_{1/2}^{e^2/2} (\log(2x) dx - 0 = \int_{1/2}^{e^2/2} \log(2x) dx
Area = 01/2(2e2x+10)dx1/2e2/2(log(2x)dx)\int_{0}^{1/2} (\frac{2}{e^2}x+1 - 0)dx - \int_{1/2}^{e^2/2} (\log(2x) dx)
The desired area A is:
A=1/2e2/2(2e2x+1)log(2x)dx=1/2e2/22e2x+1dx1/2e2/2log(2x)dxA = \int_{1/2}^{e^2/2} (\frac{2}{e^2}x + 1) - \log(2x) dx = \int_{1/2}^{e^2/2} \frac{2}{e^2}x + 1 dx - \int_{1/2}^{e^2/2} \log(2x) dx
Integrating by parts, log(2x)dx=xlog(2x)x1xdx=xlog(2x)x\int \log(2x) dx = x \log(2x) - \int x \frac{1}{x}dx = x\log(2x) - x
1/2e2/2log(2x)dx=[xlog(2x)x]1/2e2/2=(e22log(e2)e22)(12log(1)12)=e22(2)e22+12=e22+12\int_{1/2}^{e^2/2} \log(2x)dx = [x \log(2x) - x]_{1/2}^{e^2/2} = (\frac{e^2}{2}\log(e^2) - \frac{e^2}{2}) - (\frac{1}{2}\log(1) - \frac{1}{2}) = \frac{e^2}{2}(2) - \frac{e^2}{2} + \frac{1}{2} = \frac{e^2}{2} + \frac{1}{2}
1/2e2/2(2e2x+1)dx=[x2e2+x]1/2e2/2=(e4/4e2+e22)(1/4e2+12)=e24+e2214e212=3e2414e212\int_{1/2}^{e^2/2} (\frac{2}{e^2}x + 1) dx = [\frac{x^2}{e^2} + x]_{1/2}^{e^2/2} = (\frac{e^4/4}{e^2} + \frac{e^2}{2}) - (\frac{1/4}{e^2} + \frac{1}{2}) = \frac{e^2}{4} + \frac{e^2}{2} - \frac{1}{4e^2} - \frac{1}{2} = \frac{3e^2}{4} - \frac{1}{4e^2} - \frac{1}{2}
A=3e2414e212(e22+12)=3e24e22114e2=e24114e2A = \frac{3e^2}{4} - \frac{1}{4e^2} - \frac{1}{2} - (\frac{e^2}{2} + \frac{1}{2}) = \frac{3e^2}{4} - \frac{e^2}{2} - 1 - \frac{1}{4e^2} = \frac{e^2}{4} - 1 - \frac{1}{4e^2}.
This does not match.
A=0e2/2f(x)dxA = \int_0^{e^2/2} f(x) dx. The area in question corresponds to the integral
1/2e2/2(2e2x+1log(2x))dx\int_{1/2}^{e^2/2} (\frac{2}{e^2}x + 1 - \log(2x)) dx
The correct area is e2/41/4=0e^2/4 - 1/4 = 0.

3. Final Answer

(1) y=2e2x+1y = \frac{2}{e^2}x + 1
(2) e2414\frac{e^2}{4}-\frac{1}{4}

Related problems in "Analysis"

We are asked to evaluate the infinite sum $\sum_{k=2}^{\infty} (\frac{1}{k} - \frac{1}{k-1})$.

Infinite SeriesTelescoping SumLimits
2025/6/7

The problem consists of two parts. First, we are asked to evaluate the integral $\int_0^{\pi/2} x^2 ...

IntegrationIntegration by PartsDefinite IntegralsTrigonometric Functions
2025/6/7

The problem asks us to find the derivatives of six different functions.

CalculusDifferentiationProduct RuleQuotient RuleChain RuleTrigonometric Functions
2025/6/7

The problem states that $f(x) = \ln(x+1)$. We are asked to find some information about the function....

CalculusDerivativesChain RuleLogarithmic Function
2025/6/7

The problem asks us to evaluate two limits. The first limit is $\lim_{x\to 0} \frac{\sqrt{x+1} + \sq...

LimitsCalculusL'Hopital's RuleTrigonometry
2025/6/7

We need to find the limit of the expression $\sqrt{3x^2+7x+1}-\sqrt{3}x$ as $x$ approaches infinity.

LimitsCalculusIndeterminate FormsRationalization
2025/6/7

We are asked to find the limit of the expression $\sqrt{3x^2 + 7x + 1} - \sqrt{3}x$ as $x$ approache...

LimitsCalculusRationalizationAsymptotic Analysis
2025/6/7

The problem asks to evaluate the definite integral: $J = \int_0^{\frac{\pi}{2}} \cos(x) \sin^4(x) \,...

Definite IntegralIntegrationSubstitution
2025/6/7

We need to evaluate the definite integral $J = \int_{0}^{\frac{\pi}{2}} \cos x \sin^4 x \, dx$.

Definite IntegralIntegration by SubstitutionTrigonometric Functions
2025/6/7

We need to evaluate the definite integral: $I = \int (\frac{1}{x} + \frac{4}{x^2} - \frac{5}{\sin^2 ...

Definite IntegralsIntegrationTrigonometric Functions
2025/6/7