Math Problem Statement

Use implicit differentiation to find an equation of the tangent line to the curve at the given point. x2/3 + y2/3 = 4 (−3

3 , 1) (astroid)

Solution

We are tasked with finding the equation of the tangent line to the curve given by x2/3+y2/3=4x^{2/3} + y^{2/3} = 4 at the point (3,1)(-3, 1). To do this, we will use implicit differentiation.

Step-by-step Solution:

  1. Differentiate implicitly the given equation with respect to xx: x2/3+y2/3=4x^{2/3} + y^{2/3} = 4

    Taking the derivative of both sides with respect to xx, we use the chain rule for the term involving yy, as yy is a function of xx:

    ddx(x2/3)+ddx(y2/3)=0\frac{d}{dx}\left( x^{2/3} \right) + \frac{d}{dx}\left( y^{2/3} \right) = 0

  2. Differentiate each term:

    • For x2/3x^{2/3}, the derivative is: ddx(x2/3)=23x1/3\frac{d}{dx}\left( x^{2/3} \right) = \frac{2}{3}x^{-1/3}
    • For y2/3y^{2/3}, applying the chain rule: ddx(y2/3)=23y1/3dydx\frac{d}{dx}\left( y^{2/3} \right) = \frac{2}{3}y^{-1/3} \cdot \frac{dy}{dx}

    So the equation becomes: 23x1/3+23y1/3dydx=0\frac{2}{3}x^{-1/3} + \frac{2}{3}y^{-1/3} \cdot \frac{dy}{dx} = 0

  3. Solve for dydx\frac{dy}{dx}: First, subtract 23x1/3\frac{2}{3}x^{-1/3} from both sides: 23y1/3dydx=23x1/3\frac{2}{3}y^{-1/3} \cdot \frac{dy}{dx} = -\frac{2}{3}x^{-1/3}

    Cancel the 23\frac{2}{3} terms: y1/3dydx=x1/3y^{-1/3} \cdot \frac{dy}{dx} = -x^{-1/3}

    Now, solve for dydx\frac{dy}{dx}: dydx=x1/3y1/3=(yx)1/3\frac{dy}{dx} = -\frac{x^{-1/3}}{y^{-1/3}} = -\left(\frac{y}{x}\right)^{1/3}

  4. Substitute the point (3,1)(-3, 1) to find the slope of the tangent line at that point: dydx=(13)1/3=(13)1/3\frac{dy}{dx} = -\left(\frac{1}{-3}\right)^{1/3} = -(-\frac{1}{3})^{1/3}

    Since the cube root of 13-\frac{1}{3} is still 13-\frac{1}{3}, we have: dydx=13\frac{dy}{dx} = \frac{1}{3}

  5. Equation of the tangent line: The slope of the tangent line at the point (3,1)(-3, 1) is 13\frac{1}{3}, and we use the point-slope form of the line equation: yy1=m(xx1)y - y_1 = m(x - x_1) Substituting m=13m = \frac{1}{3}, (x1,y1)=(3,1)(x_1, y_1) = (-3, 1): y1=13(x+3)y - 1 = \frac{1}{3}(x + 3) Simplifying: y1=13x+1y - 1 = \frac{1}{3}x + 1 y=13x+2y = \frac{1}{3}x + 2

Final Answer:

The equation of the tangent line at the point (3,1)(-3, 1) is: y=13x+2y = \frac{1}{3}x + 2

Would you like any further clarifications or details?


Relative Questions:

  1. What is implicit differentiation and when is it used?
  2. How does the chain rule apply in implicit differentiation?
  3. What is the general form of the equation for a tangent line?
  4. How do you differentiate terms like xnx^{n} and yny^{n} implicitly?
  5. How does the cube root impact the differentiation of a function?

Tip: Always remember to apply the chain rule when differentiating implicitly, as it accounts for dependent variables like y(x)y(x).

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Derivatives
Tangent Line
Algebraic Curves

Formulas

Implicit differentiation of x^(n) and y^(n): d/dx(x^(n)) = nx^(n-1), d/dx(y^(n)) = ny^(n-1) * dy/dx
Point-slope form of a line: y - y1 = m(x - x1)

Theorems

Chain Rule
Implicit Function Theorem

Suitable Grade Level

Grade 11-12 (High School Calculus) or Introductory College Level