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Math
Posted 10 months ago
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limx0exesinxxsinx\lim _{x \rightarrow 0} \frac{e^{x}-e^{\sin x}}{x-\sin x}
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Answer from Sia
Posted 10 months ago
Solution by Steps
step 1
To find the limit of the given function as x x approaches 0, we can use L'Hôpital's Rule, which states that if the limit of functions f(x) f(x) and g(x) g(x) as x x approaches a point c c results in an indeterminate form 00 \frac{0}{0} or \frac{\infty}{\infty} , then the limit of f(x)g(x) \frac{f(x)}{g(x)} as x x approaches c c is the same as the limit of f(x)g(x) \frac{f'(x)}{g'(x)} as x x approaches c c , provided that the latter limit exists
step 2
The function exesin(x)xsin(x) \frac{e^x - e^{\sin(x)}}{x - \sin(x)} is in the indeterminate form 00 \frac{0}{0} as x x approaches 0. Applying L'Hôpital's Rule, we differentiate the numerator and the denominator with respect to x x
step 3
The derivative of the numerator exesin(x) e^x - e^{\sin(x)} with respect to x x is exesin(x)cos(x) e^x - e^{\sin(x)}\cos(x) , and the derivative of the denominator xsin(x) x - \sin(x) with respect to x x is 1cos(x) 1 - \cos(x)
step 4
Taking the limit of the derivatives as x x approaches 0, we get limx0exesin(x)cos(x)1cos(x)=110=0 \lim_{x \to 0} \frac{e^x - e^{\sin(x)}\cos(x)}{1 - \cos(x)} = \frac{1 - 1}{0} = 0 . However, this is not the final answer, as we need to apply L'Hôpital's Rule again because we still have an indeterminate form 00 \frac{0}{0}
step 5
Differentiating the numerator and the denominator again, we get limx0ex(esin(x)cos(x))(1cos(x)) \lim_{x \to 0} \frac{e^x - (e^{\sin(x)}\cos(x))'}{(1 - \cos(x))'} . The derivative of esin(x)cos(x) e^{\sin(x)}\cos(x) is esin(x)(sin(x)cos(x)+cos2(x)) e^{\sin(x)}(-\sin(x)\cos(x) + \cos^2(x)) , and the derivative of 1cos(x) 1 - \cos(x) is sin(x) \sin(x)
step 6
Taking the limit of the new derivatives as x x approaches 0, we get limx0exesin(x)(sin(x)cos(x)+cos2(x))sin(x) \lim_{x \to 0} \frac{e^x - e^{\sin(x)}(-\sin(x)\cos(x) + \cos^2(x))}{\sin(x)} . As x x approaches 0, ex e^x and esin(x) e^{\sin(x)} both approach 1, sin(x) \sin(x) approaches 0, and cos(x) \cos(x) approaches 1
step 7
Simplifying the expression, we get limx01(1)(0+1)0=limx0110=0 \lim_{x \to 0} \frac{1 - (1)(0 + 1)}{0} = \lim_{x \to 0} \frac{1 - 1}{0} = 0 . However, this is still an indeterminate form, so we apply L'Hôpital's Rule one more time
step 8
Differentiating the numerator and the denominator one more time, we get limx0ex(esin(x)(sin(x)cos(x)+cos2(x)))sin(x) \lim_{x \to 0} \frac{e^x - (e^{\sin(x)}(-\sin(x)\cos(x) + \cos^2(x)))'}{\sin(x)'} . The derivative of sin(x) \sin(x) is cos(x) \cos(x) , and the derivative of the numerator simplifies to ex e^x as x x approaches 0
step 9
Taking the limit of the final derivatives as x x approaches 0, we get limx0excos(x)=11=1 \lim_{x \to 0} \frac{e^x}{\cos(x)} = \frac{1}{1} = 1 . This is the final result of the limit
Answer
limx0exesin(x)xsin(x)=1 \lim_{x \to 0} \frac{e^x - e^{\sin(x)}}{x - \sin(x)} = 1
Key Concept
L'Hôpital's Rule and Taylor Series Expansion
Explanation
The limit was evaluated using L'Hôpital's Rule, which involves taking derivatives of the numerator and denominator until the indeterminate form is resolved. Additionally, the Taylor series expansion of ex e^x and esin(x) e^{\sin(x)} around x=0 x = 0 confirms that the leading terms cancel out, leaving the constant term 1 as x x approaches 0.

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