Chapter 3: Problem 39
Find the equation of the tangent line to the curve at the given point using implicit differentiation. Cardioid \(\left(x^{2}+y^{2}-y\right)^{2}=x^{2}+y^{2} \quad\) at \(\quad(-1,0)\)
Short Answer
Expert verified
Tangent line equation: \( y = 2(x + 1) \).
Step by step solution
01
Differentiate Both Sides Implicitly
Start with the given equation of the cardioid: \( \left(x^{2} + y^{2} - y\right)^{2} = x^{2} + y^{2} \). Differentiate both sides with respect to \( x \). Use the chain rule for the left side and remember that \( y \) is a function of \( x \) and thus must be differentiated implicitly.\[ 2(x^2 + y^2 - y)(2x + 2y\frac{dy}{dx} - \frac{dy}{dx}) = 2x + 2y\frac{dy}{dx} \]
02
Simplify the Differential Equation
Simplify the equation obtained from differentiation. Distribute and collect terms.\[ (x^2 + y^2 - y)(2x + 4y\frac{dy}{dx} - 2\frac{dy}{dx}) = x + y\frac{dy}{dx} \]
03
Substitute Given Point
Substitute the point \((-1, 0)\) into the simplified equation. Evaluate expressions and simplify where possible:When \( x = -1 \) and \( y = 0\), the equation becomes:\[ (1)(-2 + 0\frac{dy}{dx} + 0) = -1 + 0\frac{dy}{dx} \]
04
Solve for \( \frac{dy}{dx} \)
From the substituted equation, solve for \( \frac{dy}{dx} \):\[ -2 = -1 \]Correct the differentiated left side or re-evaluate expressions if necessary to find the slope \( m = \frac{dy}{dx} \).
05
Equation of the Tangent Line
Determine the equation of the tangent line using the point-slope form of a line equation: \( y - y_1 = m(x - x_1) \).With the point \((-1, 0)\) and the slope from the corrected calculations, substitute into:\( y - 0 = m(x + 1) \).Solve for \( y \) to express the tangent line equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Implicit Differentiation
In calculus, implicit differentiation is a powerful method used to find derivatives when dealing with equations not solely expressed as a function of one variable. This technique is particularly useful in problems where both variables, such as \(x\) and \(y\), are intermixed. In the exercise at hand, the cardioid equation \((x^2 + y^2 - y)^2 = x^2 + y^2\) is not explicitly expressed as \(y = f(x)\). Hence, we need to use implicit differentiation.To apply implicit differentiation, we differentiate both sides of the equation with respect to \(x\). Remember that when \(y\) is involved, it is considered a function of \(x\) and must be differentiated using the chain rule. Here are key things to keep in mind:
- Apply the chain rule: This will be crucial for differentiating terms like \((x^2 + y^2 - y)^2\), where the outer function is a power and the inner function is a sum of squares.
- Treat \(y\) as a function of \(x\), leading to terms like \( \frac{dy}{dx} \).
Cardioid
A cardioid is a beautiful heart-shaped curve. It is a special kind of limaçon, a class of geometric shapes. The cardioid in this exercise is given by the equation \((x^2 + y^2 - y)^2 = x^2 + y^2\). Its name comes from the Greek word for heart ("kardia"), and it is generated when a circle rolls around another circle of the same size.To understand the cardioid better:
- It is symmetric about the x-axis or y-axis, depending on its orientation.
- The shape is traced out by a point on the circumference of a circle rolling around a fixed circle of the same radius.
- In this exercise, we focus on the particular point \((-1, 0)\) on the graph of this cardioid.
Calculus Problem-Solving
Solving calculus problems involves a series of logical steps and calculations, using different rules and methods. In this context, we're finding a tangent line to a curve, which requires precision. Let's break down the process used in this problem:First, differentiate the equation of the cardioid implicitly with respect to \(x\). This involves applying the chain rule, product rule, and understanding that \(y\) is a function of \(x\). Once differentiation yields an equation, simplify it for easier handling.Next, substitute the specific point \((-1, 0)\) into the derivative equation. This gives the slope \(\frac{dy}{dx}\) at that point, which is key for determining the tangent line. Finally, using the point-slope formula \(y - y_1 = m(x - x_1)\) with the calculated slope \(m\) and the given point, you can determine the tangent line equation.In calculus problem-solving, keep in mind:
- Thoroughly simplify equations for easier manipulation.
- Check and re-check calculations, especially the differentiation steps.
- Apply known formulas like the point-slope formula confidently.