Chapter 3: Problem 14
Implicit differentiation Use implicit differentiation to find \(\frac{d y}{d x}\). $$e^{x y}=2 y$$
Short Answer
Expert verified
Answer: The derivative of y with respect to x is $\frac{dy}{dx} = 0$.
Step by step solution
01
Differentiate both sides of the equation with respect to x
Apply \(\frac{d}{dx}\) to both sides of the equation:
$$\frac{d}{dx} (e^{x y}) = \frac{d}{dx} (2 y)$$
02
Apply the chain rule for the left side and differentiate the right side
For the left side, by applying the chain rule for the term e^{xy}, we have:
$$\frac{d}{dx} (e^{xy}) = (e^{xy})\left(\frac{d}{dx} (xy)\right)$$
For the right side, differentiate 2y with respect to x, treating y as a function of x:
$$\frac{d}{dx} (2y) = 2\frac{dy}{dx}$$
03
Differentiate the inner function (xy) and substitute back
Differentiate xy with respect to x, treating y as a function of x, by using the product rule:
$$\frac{d}{dx}(xy) = x\frac{dy}{dx}+y$$
Substitute this expression back into the left side of step 2:
$$(e^{xy})\left(x\frac{dy}{dx}+y\right)=2\frac{dy}{dx}$$
04
Solve for \(\frac{dy}{dx}\)
Arrange the equation to solve for \(\frac{dy}{dx}\):
$$\frac{dy}{dx}(xe^{xy})+\frac{dy}{dx}(ye^{xy})-2\frac{dy}{dx}=0$$
Factor out the \(\frac{dy}{dx}\) term:
$$\frac{dy}{dx}(xe^{xy}+ye^{xy}-2)=0$$
Now divide by the factor (xe^{xy}+ye^{xy}-2) to solve for \(\frac{dy}{dx}\):
$$\frac{dy}{dx}=\frac{0}{xe^{xy}+ye^{xy}-2}$$
Thus, the derivative of y with respect to x is:
$$\frac{dy}{dx}=0$$
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chain Rule
Implicit differentiation, especially in exercises involving exponential functions such as \( e^{x y} = 2y \), requires the adept use of the Chain Rule. The Chain Rule is essential in calculus for functions composed of other functions.
Remember, when differentiating a composite function, like \( e^{xy} \), we first take the derivative of the outer function and multiply it by the derivative of the inner function.
Remember, when differentiating a composite function, like \( e^{xy} \), we first take the derivative of the outer function and multiply it by the derivative of the inner function.
- With \( e^{xy} \), the outer function is \( e^u \) (where \( u = xy \)), which differentiates to \( e^{u} \), maintaining the original expression.
- The inner derivative, \( \frac{d}{dx} (xy) \), requires further differentiation, which leads us to the next key tool: the Product Rule.
Product Rule
Using the Product Rule is crucial when differentiating terms such as \( xy \) within the larger context of implicit differentiation. This rule helps when a function is the product of two separate functions of the independent variable.
In the expression \( x y \), consider \( x \) and \( y \) as two such functions. The Product Rule states: if \( u(x) \) and \( v(x) \) are functions of \( x \), then \( \frac{d}{dx}(uv) = u'v + uv' \).
In the expression \( x y \), consider \( x \) and \( y \) as two such functions. The Product Rule states: if \( u(x) \) and \( v(x) \) are functions of \( x \), then \( \frac{d}{dx}(uv) = u'v + uv' \).
- For \( xy \), \( u(x) = x \) and \( v(x) = y \).
- The derivative \( \frac{d}{dx}(xy) \) becomes \( x \frac{dy}{dx} + y \), thus allowing us to correctly address the impact on the derivative.
Calculus Differentiation
Differentiation is foundational to calculus, offering a toolkit for addressing complex functions. Implicit differentiation is a technique used when it's problematic to separate the dependent variable on one side.
This method typically involves differentiating both sides with respect to \( x \) concurrently.
This method typically involves differentiating both sides with respect to \( x \) concurrently.
- The given equation \( e^{x y} = 2y \) exemplifies a situation where \( y \) is not easily separated.
- This calls for differentiating both sides, applying necessary rules like the Chain and Product rules.Achieving implicit differentiation leads to solving for \( \frac{dy}{dx} \), which represents the rate of change of \( y \) with respect to \( x \).