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Question
Math
Posted 9 months ago

The shaded region is bounded by the graph of the function
f(x)=1x2+1
f(x)=\frac{1}{x^{2}+1} \text {, }

the line x=kx=k, and the two coordinate axes.

If the region has area π/3\pi / 3, what is the exact value of kk ?
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Answer from Sia
Posted 9 months ago
Solution by Steps
step 1
We need to find the value of kk such that the area under the curve f(x)=1x2+1f(x) = \frac{1}{x^2 + 1} from x=0x = 0 to x=kx = k is π3\frac{\pi}{3}. This can be expressed as the definite integral: 0k1x2+1dx=π3 \int_0^k \frac{1}{x^2 + 1} \, dx = \frac{\pi}{3}
step 2
The integral of 1x2+1\frac{1}{x^2 + 1} is arctan(x)\arctan(x). Therefore, we can rewrite the integral as: [arctan(x)]0k=π3 \left[ \arctan(x) \right]_0^k = \frac{\pi}{3}
step 3
Evaluating the integral at the bounds, we get: arctan(k)arctan(0)=π3 \arctan(k) - \arctan(0) = \frac{\pi}{3}
step 4
Since arctan(0)=0\arctan(0) = 0, the equation simplifies to: arctan(k)=π3 \arctan(k) = \frac{\pi}{3}
step 5
Solving for kk, we take the tangent of both sides: k=tan(π3) k = \tan\left(\frac{\pi}{3}\right)
step 6
We know that tan(π3)=3\tan\left(\frac{\pi}{3}\right) = \sqrt{3}, so: k=3 k = \sqrt{3}
Answer
k=3k = \sqrt{3}
Key Concept
Definite Integral
Explanation
The definite integral of a function over an interval gives the area under the curve of that function over that interval. In this problem, we used the integral of 1x2+1\frac{1}{x^2 + 1} to find the value of kk that results in a specific area.

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