Calculus Examples

$x^{2} - y^{2} = 36$ , $(6, 0)$

Step 1

Find the first derivative and evaluate at $x = 6$ and $y = 0$ to find the slope of the tangent line.

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Step 1.1

Differentiate both sides of the equation.

$\frac{d}{d x} (x^{2} - y^{2}) = \frac{d}{d x} (36)$

Step 1.2

Differentiate the left side of the equation.

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Step 1.2.1

Differentiate.

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Step 1.2.1.1

By the Sum Rule, the derivative of $x^{2} - y^{2}$ with respect to $x$ is $\frac{d}{d x} [x^{2}] + \frac{d}{d x} [- y^{2}]$ .

$\frac{d}{d x} [x^{2}] + \frac{d}{d x} [- y^{2}]$

Step 1.2.1.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$2 x + \frac{d}{d x} [- y^{2}]$

Step 1.2.2

Evaluate $\frac{d}{d x} [- y^{2}]$ .

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Step 1.2.2.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- y^{2}$ with respect to $x$ is $- \frac{d}{d x} [y^{2}]$ .

$2 x - \frac{d}{d x} [y^{2}]$

Step 1.2.2.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{2}$ and $g (x) = y$ .

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Step 1.2.2.2.1

To apply the Chain Rule, set $u$ as $y$ .

$2 x - (\frac{d}{d u} [u^{2}] \frac{d}{d x} [y])$

Step 1.2.2.2.2

Differentiate using the Power Rule which states that $\frac{d}{d u} [u^{n}]$ is $n u^{n - 1}$ where $n = 2$ .

$2 x - (2 u \frac{d}{d x} [y])$

Step 1.2.2.2.3

Replace all occurrences of $u$ with $y$ .

$2 x - (2 y \frac{d}{d x} [y])$

Step 1.2.2.3

Rewrite $\frac{d}{d x} [y]$ as $y'$ .

$2 x - (2 y y')$

Step 1.2.2.4

Multiply $2$ by $- 1$ .

$2 x - 2 y y'$

Step 1.2.3

Reorder terms.

$- 2 y y' + 2 x$

Step 1.3

Since $36$ is constant with respect to $x$ , the derivative of $36$ with respect to $x$ is $0$ .

$0$

Step 1.4

Reform the equation by setting the left side equal to the right side.

$- 2 y y' + 2 x = 0$

Step 1.5

Solve for $y'$ .

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Step 1.5.1

Subtract $2 x$ from both sides of the equation.

$- 2 y y' = - 2 x$

Step 1.5.2

Divide each term in $- 2 y y' = - 2 x$ by $- 2 y$ and simplify.

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Step 1.5.2.1

Divide each term in $- 2 y y' = - 2 x$ by $- 2 y$ .

$\frac{- 2 y y'}{- 2 y} = \frac{- 2 x}{- 2 y}$

Step 1.5.2.2

Simplify the left side.

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Step 1.5.2.2.1

Cancel the common factor of $- 2$ .

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Step 1.5.2.2.1.1

Cancel the common factor.

$\frac{- 2 y y'}{- 2 y} = \frac{- 2 x}{- 2 y}$

Step 1.5.2.2.1.2

Rewrite the expression.

$\frac{y y'}{y} = \frac{- 2 x}{- 2 y}$

Step 1.5.2.2.2

Cancel the common factor of $y$ .

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Step 1.5.2.2.2.1

Cancel the common factor.

$\frac{y y'}{y} = \frac{- 2 x}{- 2 y}$

Step 1.5.2.2.2.2

Divide $y'$ by $1$ .

$y' = \frac{- 2 x}{- 2 y}$

Step 1.5.2.3

Simplify the right side.

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Step 1.5.2.3.1

Cancel the common factor of $- 2$ .

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Step 1.5.2.3.1.1

Cancel the common factor.

$y' = \frac{- 2 x}{- 2 y}$

Step 1.5.2.3.1.2

Rewrite the expression.

$y' = \frac{x}{y}$

Step 1.6

Replace $y'$ with $\frac{d y}{d x}$ .

$\frac{d y}{d x} = \frac{x}{y}$

Step 1.7

Evaluate at $x = 6$ and $y = 0$ .

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Step 1.7.1

Replace the variable $x$ with $6$ in the expression.

$\frac{6}{y}$

Step 1.7.2

Replace the variable $y$ with $0$ in the expression.

$\frac{6}{0}$

Step 1.7.3

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

Undefined

Step 2

The slope of the line is undefined, which means that it is perpendicular to the x-axis at $x = 6$ .

$x = 6$

Step 3