Approximate ln1.5 to four decimal places using the third-degree Taylor polynomial for f(x)=lnx.
A
0.0417
B
0.4167
C
0.125
D
0.6667
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1
Step 1: Recall the Taylor polynomial formula for approximating a function. The third-degree Taylor polynomial for a function f(x) centered at a point a is given by: P₃(x) = f(a) + f'(a)(x - a) + (f''(a)/2!)(x - a)² + (f'''(a)/3!)(x - a)³.
Step 2: Identify the function f(x) = ln(x) and the center point a = 1. Compute the derivatives of f(x): f'(x) = 1/x, f''(x) = -1/x², and f'''(x) = 2/x³.
Step 3: Evaluate the function and its derivatives at a = 1. This gives: f(1) = ln(1) = 0, f'(1) = 1/1 = 1, f''(1) = -1/1² = -1, and f'''(1) = 2/1³ = 2.
Step 4: Substitute these values into the Taylor polynomial formula. For x = 1.5, the polynomial becomes: P₃(1.5) = f(1) + f'(1)(1.5 - 1) + (f''(1)/2!)(1.5 - 1)² + (f'''(1)/3!)(1.5 - 1)³.
Step 5: Simplify the expression step by step. Compute (1.5 - 1), (1.5 - 1)², and (1.5 - 1)³, then substitute these values into the polynomial to approximate ln(1.5) to four decimal places.