Calculus Examples

$lim_{x \to 0} \frac{x}{\tan (x)}$

Step 1

Apply L'Hospital's rule.

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Step 1.1

Evaluate the limit of the numerator and the limit of the denominator.

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Step 1.1.1

Take the limit of the numerator and the limit of the denominator.

$\frac{lim_{x \to 0} x}{lim_{x \to 0} \tan (x)}$

Step 1.1.2

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{0}{lim_{x \to 0} \tan (x)}$

Step 1.1.3

Evaluate the limit of the denominator.

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Step 1.1.3.1

Move the limit inside the trig function because tangent is continuous.

$\frac{0}{\tan (lim_{x \to 0} x)}$

Step 1.1.3.2

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{0}{\tan (0)}$

Step 1.1.3.3

The exact value of $\tan (0)$ is $0$ .

$\frac{0}{0}$

Step 1.1.3.4

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 1.1.4

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 1.2

Since $\frac{0}{0}$ is of indeterminate form, apply L'Hospital's Rule. L'Hospital's Rule states that the limit of a quotient of functions is equal to the limit of the quotient of their derivatives.

$lim_{x \to 0} \frac{x}{\tan (x)} = lim_{x \to 0} \frac{\frac{d}{d x} [x]}{\frac{d}{d x} [\tan (x)]}$

Step 1.3

Find the derivative of the numerator and denominator.

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Step 1.3.1

Differentiate the numerator and denominator.

$lim_{x \to 0} \frac{\frac{d}{d x} [x]}{\frac{d}{d x} [\tan (x)]}$

Step 1.3.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$lim_{x \to 0} \frac{1}{\frac{d}{d x} [\tan (x)]}$

Step 1.3.3

The derivative of $\tan (x)$ with respect to $x$ is $\sec^{2} (x)$ .

$lim_{x \to 0} \frac{1}{\sec^{2} (x)}$

Step 2

Evaluate the limit.

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Step 2.1

Split the limit using the Limits Quotient Rule on the limit as $x$ approaches $0$ .

$\frac{lim_{x \to 0} 1}{lim_{x \to 0} \sec^{2} (x)}$

Step 2.2

Evaluate the limit of $1$ which is constant as $x$ approaches $0$ .

$\frac{1}{lim_{x \to 0} \sec^{2} (x)}$

Step 2.3

Move the exponent $2$ from $\sec^{2} (x)$ outside the limit using the Limits Power Rule.

$\frac{1}{{(lim_{x \to 0} \sec (x))}^{2}}$

Step 2.4

Move the limit inside the trig function because secant is continuous.

$\frac{1}{\sec^{2} (lim_{x \to 0} x)}$

Step 3

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{1}{\sec^{2} (0)}$

Step 4

Simplify the answer.

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Step 4.1

Rewrite $1$ as $1^{2}$ .

$\frac{1^{2}}{\sec^{2} (0)}$

Step 4.2

Rewrite $\frac{1^{2}}{\sec^{2} (0)}$ as ${(\frac{1}{\sec (0)})}^{2}$ .

${(\frac{1}{\sec (0)})}^{2}$

Step 4.3

Rewrite $\sec (0)$ in terms of sines and cosines.

${(\frac{1}{\frac{1}{\cos (0)}})}^{2}$

Step 4.4

Multiply by the reciprocal of the fraction to divide by $\frac{1}{\cos (0)}$ .

${(1 \cos (0))}^{2}$

Step 4.5

Multiply $\cos (0)$ by $1$ .

$\cos^{2} (0)$

Step 4.6

The exact value of $\cos (0)$ is $1$ .

$1^{2}$

Step 4.7

One to any power is one.

$1$