2. Use implicit differentiation to find y' for the curve. cos x sin y = 1/4

Calculus For The Life Sciences
2nd Edition
ISBN:9780321964038
Author:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Publisher:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Chapter6: Applications Of The Derivative
Section6.CR: Chapter 6 Review
Problem 48CR
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### Problem Statement

**2. Use implicit differentiation to find \( y' \) for the curve:**

\[ \cos x \sin y = \frac{1}{4} \]

### Explanation

To solve this problem, you need to use the technique of implicit differentiation. In implicit differentiation, both \( x \) and \( y \) are functions of some variable, often \( t \). The following steps outline the process:

1. **Differentiate both sides of the equation with respect to \( x \)**:

   Given:
   \[ \cos x \sin y = \frac{1}{4} \]

   Differentiate using the product rule on the left side:
   \[ \frac{d}{dx} (\cos x \sin y) = \frac{d}{dx} \frac{1}{4} \]

2. **Apply the product rule and chain rule**:

   Recall that the product rule states \( \frac{d}{dx} [u v] = u'v + uv' \), and the chain rule is used when differentiating a composite function.

   Here:
   \[ \frac{d}{dx} (\cos x \sin y) = (\frac{d}{dx} \cos x) \sin y + \cos x \frac{d}{dx} \sin y \]
   
   Using the derivatives:
   \[ \frac{d}{dx} (\cos x) = -\sin x \]
   \[ \frac{d}{dx} (\sin y) = \cos y \cdot \frac{dy}{dx} = \cos y \cdot y'\]

   Substituting these back in:
   \[  -\sin x \sin y + \cos x \cos y \frac{dy}{dx} = 0 \]

3. **Solve for \( y' \)**:

   \[ \cos x \cos y \frac{dy}{dx} = \sin x \sin y \]
   \[ \frac{dy}{dx} = y' = \frac{\sin x \sin y}{\cos x \cos y} \]
   \[ y' = \tan x \tan y \]

Thus, the derivative \( y' \) for the given curve using implicit differentiation is:
\[ y' = \tan x \tan y \]
Transcribed Image Text:### Problem Statement **2. Use implicit differentiation to find \( y' \) for the curve:** \[ \cos x \sin y = \frac{1}{4} \] ### Explanation To solve this problem, you need to use the technique of implicit differentiation. In implicit differentiation, both \( x \) and \( y \) are functions of some variable, often \( t \). The following steps outline the process: 1. **Differentiate both sides of the equation with respect to \( x \)**: Given: \[ \cos x \sin y = \frac{1}{4} \] Differentiate using the product rule on the left side: \[ \frac{d}{dx} (\cos x \sin y) = \frac{d}{dx} \frac{1}{4} \] 2. **Apply the product rule and chain rule**: Recall that the product rule states \( \frac{d}{dx} [u v] = u'v + uv' \), and the chain rule is used when differentiating a composite function. Here: \[ \frac{d}{dx} (\cos x \sin y) = (\frac{d}{dx} \cos x) \sin y + \cos x \frac{d}{dx} \sin y \] Using the derivatives: \[ \frac{d}{dx} (\cos x) = -\sin x \] \[ \frac{d}{dx} (\sin y) = \cos y \cdot \frac{dy}{dx} = \cos y \cdot y'\] Substituting these back in: \[ -\sin x \sin y + \cos x \cos y \frac{dy}{dx} = 0 \] 3. **Solve for \( y' \)**: \[ \cos x \cos y \frac{dy}{dx} = \sin x \sin y \] \[ \frac{dy}{dx} = y' = \frac{\sin x \sin y}{\cos x \cos y} \] \[ y' = \tan x \tan y \] Thus, the derivative \( y' \) for the given curve using implicit differentiation is: \[ y' = \tan x \tan y \]
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