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Multiple Choice
Find the exact length of the curve for .
A
The exact length is
B
The exact length is
C
The exact length is
D
The exact length is
Verified step by step guidance
1
Step 1: Recall the formula for the arc length of a curve y = f(x) over the interval [a, b]. The arc length is given by L = ∫[a, b] √(1 + (dy/dx)^2) dx.
Step 2: Compute the derivative of y = x^3 / 3 + 1 / (4x). Use the power rule and the quotient rule to find dy/dx. For x^3 / 3, the derivative is (1/3)(3x^2) = x^2. For 1 / (4x), rewrite it as (1/4)x^(-1) and differentiate to get -1/(4x^2). Thus, dy/dx = x^2 - 1/(4x^2).
Step 3: Square the derivative dy/dx to find (dy/dx)^2. Expand (x^2 - 1/(4x^2))^2 using the binomial expansion: (dy/dx)^2 = x^4 - 2(x^2)(1/(4x^2)) + (1/(4x^2))^2. Simplify each term to get (dy/dx)^2 = x^4 - 1/2 + 1/(16x^4).
Step 4: Substitute (dy/dx)^2 into the arc length formula. The integrand becomes √(1 + x^4 - 1/2 + 1/(16x^4)). Combine terms inside the square root: √(x^4 + 1/2 + 1/(16x^4)).
Step 5: Set up the definite integral for the arc length over the interval [1, 3]. Evaluate L = ∫[1, 3] √(x^4 + 1/2 + 1/(16x^4)) dx. Simplify and solve the integral to find the exact length, which is given as (1/12) [82^{3/2} - 10^{3/2}].