Discover answers to your most pressing questions at Westonci.ca, the ultimate Q&A platform that connects you with expert solutions. Ask your questions and receive detailed answers from professionals with extensive experience in various fields. Join our platform to connect with experts ready to provide precise answers to your questions in different areas.

Use implicit differentiation to find an equation of the tangent line to the curve at the given point.

[tex]\[ x^{2 / 3}+y^{2 / 3}=4, \quad (-3 \sqrt{3}, 1) \quad \text{(astroid)} \][/tex]

Sagot :

To find the equation of the tangent line to the curve [tex]\( x^{2/3} + y^{2/3} = 4 \)[/tex] at the point [tex]\((-3\sqrt{3}, 1)\)[/tex], we will use implicit differentiation and find the slope at the given point, and then form the equation of the tangent line.

### Step-by-Step Solution:

1. Implicit Differentiation:
Begin by differentiating the given equation [tex]\( x^{2/3} + y^{2/3} = 4 \)[/tex] implicitly with respect to [tex]\( x \)[/tex].

[tex]\[ \frac{d}{dx}(x^{2/3} + y^{2/3}) = \frac{d}{dx}(4) \][/tex]

Differentiating term by term:
[tex]\[ \frac{d}{dx}(x^{2/3}) + \frac{d}{dx}(y^{2/3}) = 0 \][/tex]

Using the chain rule for the second term:
[tex]\[ \frac{2}{3}x^{-1/3} + \frac{2}{3}y^{-1/3} \frac{dy}{dx} = 0 \][/tex]

2. Solve for [tex]\(\frac{dy}{dx}\)[/tex] (Slope of Tangent Line):
Isolate [tex]\(\frac{dy}{dx}\)[/tex]:

[tex]\[ \frac{2}{3}x^{-1/3} = -\frac{2}{3}y^{-1/3} \frac{dy}{dx} \][/tex]

Simplify:

[tex]\[ x^{-1/3} = -y^{-1/3} \frac{dy}{dx} \][/tex]

Divide both sides by [tex]\( -y^{-1/3} \)[/tex]:

[tex]\[ \frac{dy}{dx} = -\frac{x^{-1/3}}{y^{-1/3}} \][/tex]

Rewrite it with positive exponents:

[tex]\[ \frac{dy}{dx} = -\frac{y^{1/3}}{x^{1/3}} \][/tex]

3. Calculate the Slope at the Given Point [tex]\( (-3\sqrt{3}, 1) \)[/tex]:
Substitute [tex]\( x = -3\sqrt{3} \)[/tex] and [tex]\( y = 1 \)[/tex] into the slope expression:

[tex]\[ \left.\frac{dy}{dx}\right|_{(-3\sqrt{3}, 1)} = -\frac{(1)^{1/3}}{(-3\sqrt{3})^{1/3}} \][/tex]

Simplify the slope calculation:

[tex]\[ (1)^{1/3} = 1 \][/tex]
[tex]\[ (-3\sqrt{3})^{1/3} = -\sqrt[3]{27} = -3^{1/3} \cdot (\sqrt{3})^{1/3} = -3 \cdot \sqrt[3]{3} \][/tex]

Therefore, the slope is:

[tex]\[ \left.\frac{dy}{dx}\right|_{(-3\sqrt{3}, 1)} = -\frac{1}{-3\sqrt[3]{3}} = \frac{1}{3\sqrt[3]{3}} \][/tex]

4. Equation of the Tangent Line:
The equation of a tangent line in point-slope form is:

[tex]\[ y - y_1 = m(x - x_1) \][/tex]

Where [tex]\( (x_1, y_1) \)[/tex] is the point [tex]\( (-3\sqrt{3}, 1) \)[/tex] and [tex]\( m \)[/tex] is the slope calculated above:

[tex]\[ y - 1 = \frac{1}{3\sqrt[3]{3}}(x + 3\sqrt{3}) \][/tex]

Simplify the equation:

[tex]\[ y - 1 = \frac{1}{3\sqrt[3]{3}} x + \frac{1}{3\sqrt[3]{3}} \cdot 3\sqrt{3} \][/tex]

Since [tex]\( \frac{1}{3\sqrt[3]{3}} \cdot 3\sqrt{3} = 1 \)[/tex]:

[tex]\[ y - 1 = \frac{1}{3\sqrt[3]{3}} x + 1 \][/tex]

Add 1 to both sides:

[tex]\[ y = \frac{1}{3\sqrt[3]{3}} x + 2 \][/tex]

Thus, the equation of the tangent line to the curve [tex]\( x^{2/3} + y^{2/3} = 4 \)[/tex] at the point [tex]\((-3\sqrt{3}, 1)\)[/tex] is:

[tex]\[ y = \frac{1}{3\sqrt[3]{3}} x + 2 \][/tex]