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Using L' Hospital's rule, evaluate: li...

Using L' Hospital's rule, evaluate:
`lim_(x to 0) ((1)/(x^(2))-(cotx)/(x))`

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To evaluate the limit using L'Hôpital's rule, we start with the expression: \[ \lim_{x \to 0} \left( \frac{1}{x^2} - \frac{\cot x}{x} \right) \] ### Step 1: Combine the fractions We can combine the two fractions into a single fraction: \[ \lim_{x \to 0} \left( \frac{1}{x^2} - \frac{\cot x}{x} \right) = \lim_{x \to 0} \left( \frac{x - x^2 \cot x}{x^2} \right) \] ### Step 2: Rewrite cotangent Recall that \(\cot x = \frac{\cos x}{\sin x}\), thus we can rewrite the limit as: \[ \lim_{x \to 0} \left( \frac{x - x^2 \frac{\cos x}{\sin x}}{x^2} \right) = \lim_{x \to 0} \left( \frac{x \sin x - x^2 \cos x}{x^2 \sin x} \right) \] ### Step 3: Simplify the expression Now, we can simplify the numerator: \[ \lim_{x \to 0} \left( \frac{x \sin x - x^2 \cos x}{x^2 \sin x} \right) \] As \(x\) approaches \(0\), both the numerator and denominator approach \(0\), which gives us the indeterminate form \(\frac{0}{0}\). ### Step 4: Apply L'Hôpital's Rule Since we have an indeterminate form, we can apply L'Hôpital's Rule. We differentiate the numerator and the denominator separately: 1. Differentiate the numerator: \[ \frac{d}{dx}(x \sin x - x^2 \cos x) = \sin x + x \cos x - (2x \cos x - x^2 \sin x) = \sin x + x \cos x - 2x \cos x + x^2 \sin x \] Simplifying gives: \[ \sin x - x \cos x + x^2 \sin x \] 2. Differentiate the denominator: \[ \frac{d}{dx}(x^2 \sin x) = 2x \sin x + x^2 \cos x \] Now we have: \[ \lim_{x \to 0} \frac{\sin x - x \cos x + x^2 \sin x}{2x \sin x + x^2 \cos x} \] ### Step 5: Evaluate the limit again Substituting \(x = 0\): - The numerator becomes: \[ \sin(0) - 0 \cdot \cos(0) + 0^2 \cdot \sin(0) = 0 \] - The denominator becomes: \[ 2 \cdot 0 \cdot \sin(0) + 0^2 \cdot \cos(0) = 0 \] This is still an indeterminate form, so we apply L'Hôpital's Rule again. ### Step 6: Differentiate again 1. Differentiate the new numerator: \[ \frac{d}{dx}(\sin x - x \cos x + x^2 \sin x) = \cos x - (\cos x - x \sin x) + (2x \sin x + x^2 \cos x) \] Simplifying gives: \[ 2x \sin x + x^2 \cos x \] 2. Differentiate the new denominator: \[ \frac{d}{dx}(2x \sin x + x^2 \cos x) = 2 \sin x + 2x \cos x + (2x \cos x - x^2 \sin x) \] Simplifying gives: \[ 4x \cos x + 2 \sin x - x^2 \sin x \] ### Step 7: Evaluate the limit again Substituting \(x = 0\): - The numerator becomes: \[ 2 \cdot 0 \cdot \sin(0) + 0^2 \cdot \cos(0) = 0 \] - The denominator becomes: \[ 4 \cdot 0 \cdot \cos(0) + 2 \cdot \sin(0) - 0^2 \cdot \sin(0) = 0 \] ### Step 8: Final differentiation Apply L'Hôpital's Rule one last time: 1. Differentiate the numerator: \[ \frac{d}{dx}(2x \sin x) = 2 \sin x + 2x \cos x \] 2. Differentiate the denominator: \[ \frac{d}{dx}(4x \cos x + 2 \sin x) = 4 \cos x - 4x \sin x + 2 \cos x = 6 \cos x - 4x \sin x \] ### Step 9: Evaluate the limit Now we can evaluate: \[ \lim_{x \to 0} \frac{2 \sin x + 2x \cos x}{6 \cos x - 4x \sin x} \] Substituting \(x = 0\): - The numerator becomes: \[ 2 \cdot \sin(0) + 2 \cdot 0 \cdot \cos(0) = 0 \] - The denominator becomes: \[ 6 \cdot \cos(0) - 4 \cdot 0 \cdot \sin(0) = 6 \] Thus, the limit evaluates to: \[ \lim_{x \to 0} \frac{0}{6} = 0 \] ### Final Answer The limit is: \[ \boxed{0} \]
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