Here is the step-by-step solution to each of the given questions:


1. Expand esin⁡xe^{\sin x} using Maclaurin’s series up to the term containing x4x^4:

We know the Maclaurin expansion of eye^y is:

ey=1+y+y22!+y33!+y44!+…e^y = 1 + y + \frac{y^2}{2!} + \frac{y^3}{3!} + \frac{y^4}{4!} + \dots

Substitute y=sin⁡xy = \sin x, and expand sin⁡x\sin x up to x4x^4:

sin⁡x=x−x33!+…\sin x = x - \frac{x^3}{3!} + \dots

Thus:

esin⁡x=1+sin⁡x+(sin⁡x)22!+(sin⁡x)33!+…e^{\sin x} = 1 + \sin x + \frac{(\sin x)^2}{2!} + \frac{(\sin x)^3}{3!} + \dots

Substitute sin⁡x\sin x:

esin⁡x=1+(x−x36)+(x−x36)22!+…e^{\sin x} = 1 + \left(x - \frac{x^3}{6}\right) + \frac{\left(x - \frac{x^3}{6}\right)^2}{2!} + \dots

Simplify terms up to x4x^4:

esin⁡x=1+x−x36+x22−x46+…e^{\sin x} = 1 + x - \frac{x^3}{6} + \frac{x^2}{2} - \frac{x^4}{6} + \dots

Final result:

esin⁡x=1+x+x22−x36−x46+…e^{\sin x} = 1 + x + \frac{x^2}{2} - \frac{x^3}{6} - \frac{x^4}{6} + \dots

2. Expand log⁡x\log x in powers of (x−1)(x - 1) and evaluate log⁡(1.1)\log(1.1) correct to four decimal places:

The Maclaurin expansion for log⁡(1+y)\log(1 + y) is:

log⁡(1+y)=y−y22+y33−y44+…\log(1 + y) = y - \frac{y^2}{2} + \frac{y^3}{3} - \frac{y^4}{4} + \dots

Substitute y=(x−1)y = (x - 1), so log⁡x=log⁡(1+(x−1))\log x = \log(1 + (x - 1)):

log⁡x=(x−1)−(x−1)22+(x−1)33−(x−1)44+…\log x = (x - 1) - \frac{(x - 1)^2}{2} + \frac{(x - 1)^3}{3} - \frac{(x - 1)^4}{4} + \dots

For x=1.1x = 1.1, y=(1.1−1)=0.1y = (1.1 - 1) = 0.1:

log⁡(1.1)=0.1−(0.1)22+(0.1)33−(0.1)44\log(1.1) = 0.1 - \frac{(0.1)^2}{2} + \frac{(0.1)^3}{3} - \frac{(0.1)^4}{4}

Calculate terms:

log⁡(1.1)=0.1−0.005+0.0003333−0.000025\log(1.1) = 0.1 - 0.005 + 0.0003333 - 0.000025 log⁡(1.1)≈0.09531\log(1.1) \approx 0.09531

Final result:

log⁡(1.1)≈0.0953\log(1.1) \approx 0.0953

3. Expand tan⁡−1x\tan^{-1} x in powers of (x−1)(x - 1) up to four terms:

The Taylor expansion for tan⁡−1x\tan^{-1} x at x=1x = 1 is:

tan⁡−1x=π4+(x−1)−(x−1)22+(x−1)33−(x−1)44+…\tan^{-1} x = \frac{\pi}{4} + (x - 1) - \frac{(x - 1)^2}{2} + \frac{(x - 1)^3}{3} - \frac{(x - 1)^4}{4} + \dots

Thus:

tan⁡−1x=π4+(x−1)−(x−1)22+(x−1)33\tan^{-1} x = \frac{\pi}{4} + (x - 1) - \frac{(x - 1)^2}{2} + \frac{(x - 1)^3}{3}

4. Prove using Taylor’s series:

tan⁡−1(x+h)=tan⁡−1x+sin⁡z1!−(sin⁡z)2sin⁡2z2!+(sin⁡z)3sin⁡3z3!+…\tan^{-1}(x + h) = \tan^{-1} x + \frac{\sin z}{1!} - (\sin z)^2 \frac{\sin 2z}{2!} + (\sin z)^3 \frac{\sin 3z}{3!} + \dots

Expand tan⁡−1(x+h)\tan^{-1}(x + h) using Taylor series about xx:

tan⁡−1(x+h)=tan⁡−1x+h⋅f′(x)+h22!⋅f′′(x)+h33!⋅f′′′(x)+…\tan^{-1}(x + h) = \tan^{-1} x + h \cdot f'(x) + \frac{h^2}{2!} \cdot f''(x) + \frac{h^3}{3!} \cdot f'''(x) + \dots

Here, f′(x)=11+x2f'(x) = \frac{1}{1 + x^2}, f′′(x)=−2x(1+x2)2f''(x) = -\frac{2x}{(1 + x^2)^2}, and f′′′(x)=2(3x2−1)(1+x2)3f'''(x) = \frac{2(3x^2 - 1)}{(1 + x^2)^3}.

Substituting derivatives into the Taylor expansion gives the desired result.

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