Math Problem Statement

if siny+x=7/2, find the rate of change at point (3,pi/6)

Solution

We are tasked with finding the rate of change of the equation sin(y)+x=72\sin(y) + x = \frac{7}{2} at the point (3,π6)(3, \frac{\pi}{6}). This involves finding the total derivative, which can be interpreted as the rate of change of yy with respect to xx.

Step 1: Implicit Differentiation

We differentiate both sides of the equation sin(y)+x=72\sin(y) + x = \frac{7}{2} with respect to xx, treating yy as a function of xx.

ddx(sin(y)+x)=ddx(72)\frac{d}{dx} \left( \sin(y) + x \right) = \frac{d}{dx} \left( \frac{7}{2} \right)

Since 72\frac{7}{2} is a constant, its derivative is 0. Now apply the derivative to each term:

  • The derivative of sin(y)\sin(y) with respect to xx is cos(y)dydx\cos(y) \cdot \frac{dy}{dx} by the chain rule.
  • The derivative of xx with respect to xx is 1.

Thus, we get the equation:

cos(y)dydx+1=0\cos(y) \cdot \frac{dy}{dx} + 1 = 0

Step 2: Solve for dydx\frac{dy}{dx}

Now, solve for dydx\frac{dy}{dx} (the rate of change of yy with respect to xx):

cos(y)dydx=1\cos(y) \cdot \frac{dy}{dx} = -1 dydx=1cos(y)\frac{dy}{dx} = \frac{-1}{\cos(y)}

Step 3: Substitute the Given Point

We are given the point (3,π6)(3, \frac{\pi}{6}), which means x=3x = 3 and y=π6y = \frac{\pi}{6}. At this point:

cos(π6)=32\cos\left( \frac{\pi}{6} \right) = \frac{\sqrt{3}}{2}

Now substitute this value into the equation for dydx\frac{dy}{dx}:

dydx=132=23\frac{dy}{dx} = \frac{-1}{\frac{\sqrt{3}}{2}} = \frac{-2}{\sqrt{3}}

Step 4: Simplify the Result

To simplify, multiply the numerator and denominator by 3\sqrt{3}:

dydx=2333=233\frac{dy}{dx} = \frac{-2}{\sqrt{3}} \cdot \frac{\sqrt{3}}{\sqrt{3}} = \frac{-2\sqrt{3}}{3}

Thus, the rate of change of yy with respect to xx at the point (3,π6)(3, \frac{\pi}{6}) is:

dydx=233\frac{dy}{dx} = \frac{-2\sqrt{3}}{3}

Do you need any further clarifications or details on this?

Related Questions:

  1. How do we apply implicit differentiation to more complex functions?
  2. What is the geometric interpretation of dydx\frac{dy}{dx} in terms of the slope of the curve?
  3. How does chain rule apply when differentiating trigonometric functions?
  4. Can we find the second derivative from the given equation?
  5. How would the rate of change differ at another point on this curve?

Tip:

Always ensure you understand the chain rule when differentiating implicitly, as it is crucial for handling functions where yy is a function of xx.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Trigonometry
Rates of Change

Formulas

Implicit differentiation: d/dx(f(y)) = f'(y) * dy/dx
Trigonometric derivative: d/dx(sin(y)) = cos(y) * dy/dx
Rate of change: dy/dx = -1 / cos(y)

Theorems

Chain Rule
Trigonometric Identities

Suitable Grade Level

Grade 12 / Early College