Use L'Hôpital's Rule (possibly more than once) to evaluate the following limit. (Use symbolic notation and fractions where needed.)limx→07x−sin(7x)sin(7x)−7xcos(7x)=
Q. Use L'Hôpital's Rule (possibly more than once) to evaluate the following limit. (Use symbolic notation and fractions where needed.)limx→07x−sin(7x)sin(7x)−7xcos(7x)=
Check Indeterminate Form: We are given the limit to evaluate using L'Hôpital's Rule:limx→07x−sin(7x)sin(7x)−7xcos(7x)First, we need to check if the limit is in an indeterminate form that allows us to apply L'Hôpital's Rule.
Evaluate Numerator and Denominator: Evaluate the limit of the numerator and the denominator separately as x approaches 0:limx→0sin(7x)=0limx→07xcos(7x)=0limx→07x=0limx→0sin(7x)=0Both the numerator and the denominator approach 0, so we have an indeterminate form of 0/0.
Apply L'Hôpital's Rule: Since we have an indeterminate form, we can apply L'Hôpital's Rule, which states that if limx→cg(x)f(x)=00 or ±∞/±∞, then limx→cg(x)f(x) can be found by limx→cg′(x)f′(x), provided the latter limit exists.
Find Derivatives: We will find the derivatives of the numerator and the denominator:The derivative of the numerator f(x)=sin(7x)−7xcos(7x) is f′(x)=7cos(7x)−7cos(7x)+49xsin(7x).The derivative of the denominator g(x)=7x−sin(7x) is g′(x)=7−7cos(7x).
Simplify Derivative: Simplify the derivative of the numerator: f′(x)=7cos(7x)−7cos(7x)+49xsin(7x) simplifies to f′(x)=49xsin(7x).
Apply Rule Again: Now we apply L'Hôpital's Rule by taking the limit of the derivatives: limx→0g′(x)f′(x)=limx→07−7cos(7x)49xsin(7x)
Find New Derivatives: Evaluate the limit of the new expression as x approaches 0: limx→0(49xsin(7x))=0 limx→0(7−7cos(7x))=0 We again have an indeterminate form of 0/0, so we need to apply L'Hôpital's Rule once more.
Evaluate New Expression: Find the derivatives of the new numerator and denominator:The derivative of the new numerator h(x)=49xsin(7x) is h′(x)=49sin(7x)+343xcos(7x).The derivative of the new denominator k(x)=7−7cos(7x) is k′(x)=7sin(7x).
Re-evaluate Derivatives: Apply L'Hôpital's Rule again by taking the limit of the new derivatives: limx→0k′(x)h′(x)=limx→0(7sin(7x))(49sin(7x)+343xcos(7x))
Re-evaluate Derivatives: Apply L'Hôpital's Rule again by taking the limit of the new derivatives: limx→0k′(x)h′(x)=limx→07sin(7x)49sin(7x)+343xcos(7x)Evaluate the limit of the new expression as x approaches 0: limx→0(49sin(7x)+343xcos(7x))=49×0+343×0×1=0limx→0(7sin(7x))=7×0=0We still have an indeterminate form of 0/0, which means we made a mistake in our differentiation or simplification. We need to re-evaluate the derivatives.
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