Question:medium

If the radius of curvature (\(\rho\)) at (0, 1) of \(y = e^x\) is \(\alpha\sqrt{\beta}\), then \(\alpha^2+\beta\) is:

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The radius of curvature formula is a standard application of differentiation. Remember to evaluate the derivatives at the specified point *before* plugging them into the formula. The expression \(2^{3/2}\) can be tricky; remember that \(x^{a/b} = (\sqrt[b]{x})^a\), so \(2^{3/2} = (\sqrt{2})^3 = 2\sqrt{2}\).
Updated On: Feb 20, 2026
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The Correct Option is B

Solution and Explanation

Step 1: Conceptual Understanding:
The radius of curvature (\(\rho\)) at a point on a curve \(y=f(x)\) signifies the radius of the circle that best approximates the curve at that location. This value must be computed for \(y=e^x\) at (0, 1), and subsequently used to determine \(\alpha\) and \(\beta\) based on a given format.

Step 2: Formula:
The radius of curvature is calculated using the formula:
\[ \rho = \frac{[1 + (y')^2]^{3/2}}{|y''|} \]
Here, \(y'\) and \(y''\) represent the first and second derivatives of \(y\) with respect to \(x\), respectively.

Step 3: Calculation Process:
1. Derivatives of \(y = e^x\):
\[ y = e^x \]
\[ y' = e^x \]
\[ y'' = e^x \]

2. Derivatives at (0, 1):
At the point (0, 1), \(x=0\).
\[ y'(0) = e^0 = 1 \]
\[ y''(0) = e^0 = 1 \]

3. Radius of Curvature \(\rho\) at (0, 1):
Substituting the evaluated derivatives into the formula:
\[ \rho = \frac{[1 + (1)^2]^{3/2}}{|1|} = \frac{[1+1]^{3/2}}{1} = 2^{3/2} \]
\[ \rho = \sqrt{2^3} = \sqrt{8} = 2\sqrt{2} \]

4. Determining \(\alpha\) and \(\beta\):
The radius of curvature is expressed in the form \(\alpha\sqrt{\beta}\).
Comparing \(\rho = 2\sqrt{2}\) with \(\alpha\sqrt{\beta}\), we obtain:
\[ \alpha = 2, \quad \beta = 2 \]

5. Calculation of \(\alpha^2 + \beta\):
\[ \alpha^2 + \beta = (2)^2 + 2 = 4 + 2 = 6 \]

Step 4: Conclusion:
The calculated value of \(\alpha^2 + \beta\) is 6.
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