Math Problem Statement

Find an equation of the tangent line to the curve x^(2/3) + y^(2/3) = 5 at the point (-8, -1).

Solution

We are tasked with finding the equation of the tangent line to the curve defined by:

x2/3+y2/3=5x^{2/3} + y^{2/3} = 5

at the point (8,1)(-8, -1).

Steps to solve this problem:

  1. Implicit Differentiation: We first differentiate both sides of the equation x2/3+y2/3=5x^{2/3} + y^{2/3} = 5 with respect to xx, keeping in mind that yy is a function of xx (implicit differentiation).

    Differentiating x2/3x^{2/3} with respect to xx: ddx(x2/3)=23x1/3\frac{d}{dx} \left( x^{2/3} \right) = \frac{2}{3}x^{-1/3}

    Differentiating y2/3y^{2/3} with respect to xx: ddx(y2/3)=23y1/3dydx\frac{d}{dx} \left( y^{2/3} \right) = \frac{2}{3}y^{-1/3} \cdot \frac{dy}{dx}

  2. Differentiation of the equation: Applying the product rule to the entire equation: 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}: Rearranging to isolate dydx\frac{dy}{dx}: 23y1/3dydx=23x1/3\frac{2}{3}y^{-1/3} \cdot \frac{dy}{dx} = -\frac{2}{3}x^{-1/3} y1/3dydx=x1/3y^{-1/3} \cdot \frac{dy}{dx} = -x^{-1/3} 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 (8,1)(-8, -1) into the derivative: At the point (8,1)(-8, -1): dydx=(18)1/3=(18)1/3=12\frac{dy}{dx} = -\left(\frac{-1}{-8}\right)^{1/3} = -\left(\frac{1}{8}\right)^{1/3} = -\frac{1}{2}

    So, the slope of the tangent line at (8,1)(-8, -1) is 12-\frac{1}{2}.

  5. Equation of the tangent line: The equation of a line is given by: yy1=m(xx1)y - y_1 = m(x - x_1) Substituting m=12m = -\frac{1}{2}, x1=8x_1 = -8, and y1=1y_1 = -1: y(1)=12(x(8))y - (-1) = -\frac{1}{2}(x - (-8)) y+1=12(x+8)y + 1 = -\frac{1}{2}(x + 8) y+1=12x4y + 1 = -\frac{1}{2}x - 4 y=12x5y = -\frac{1}{2}x - 5

Thus, the equation of the tangent line is: y=12x5y = -\frac{1}{2}x - 5

Let me know if you'd like further details or have any questions.

Here are 5 related questions to expand the concept:

  1. What is implicit differentiation and when is it used?
  2. How do you find the equation of a tangent line for parametric curves?
  3. How does the behavior of the astroid change as you vary the value in its equation?
  4. What is the geometric meaning of the slope at a given point on a curve?
  5. How does the tangent line relate to the normal line?

Tip: When differentiating implicitly, remember that every time you differentiate a term involving yy, you must multiply by dydx\frac{dy}{dx}.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Algebra
Calculus

Formulas

Implicit differentiation formula
Equation of a line: y - y1 = m(x - x1)
Slope formula from implicit differentiation

Theorems

Differentiation of implicit functions
Equation of tangent line theorem

Suitable Grade Level

Grade 11-12 (or Calculus level)