Implicit Differentiation; Tangent Line

In summary, the original equation is x^(1/3) + y^(1/3) = 4 and the point of interest is (-3√3, 1). The derivative of the equation is y' = -y^(2/3)/x^(2/3). The slope of the tangent line at the given point is -1/3.
  • #1
b521
10
0

Homework Statement


Find the equation of a tangent line at the curve at point (-3√3, 1)

x^(1/3) + y^(1/3) = 4

Homework Equations


Point-slope:
y-1=m(x-1)

The Attempt at a Solution



I took the derivative of that equation and resulted in
-y^(2/3)/x^(2/3)

When I tried plugging in x and y to get slope, the equation got very messy and I couldn't get a number out of it. Can anyone help me out?
 
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  • #2
b521 said:

Homework Statement


Find the equation of a tangent line at the curve at point (-3√3, 1)

x^(1/3) = y^(1/3) = 4
Looks like there is a typo here.
b521 said:

Homework Equations


Point-slope:
y-1=m(x-1)
This would be the line with slope m, that passes through (1, 1).
b521 said:

The Attempt at a Solution



I took the derivative of that equation and resulted in
y^(2/3)/x^(2/3)
It's hard to tell whether this is correct, since the original equation likely has a typo. If you typed '=' in place of '+', then you have a sign error in your derivative. Also, it would be helpful to have an equation for your derivative; e.g., y' = y^(2/3)/x^(2/3).
b521 said:
When I tried plugging in x and y to get slope, the equation got very messy and I couldn't get a number out of it. Can anyone help me out?
 
  • #3
Here's all of my work:

(1/3)x^(-2/3) + 1/3y^(-2/3)(dy/dx) = 0

(dy/dx)1/3y^(2/3) = -1/3x^(2/3)
dy/dx = -3y^(2/3)/3x^(2/3)
dy/dx = -y^(2/3)/x^(2/3)

I hope that helps find my problem. This is where I tried plugging in the x value and everything got complicated.

1/(-3√3)^(2/3)
 
  • #4
What is the original equation? I can't tell if your work is correct without knowing the original equation.
 
  • #5
(-3√3)^(2/3) can also be written as ((-3√3)^2)^(1/3)
 
  • #6
Mark44 said:
What is the original equation? I can't tell if your work is correct without knowing the original equation.

x^(1/3) + y^(1/3) = 4

This is the original equation. Sorry about the typo before.
 
  • #7
That's what I thought, but I wanted to make sure. You should have enough information to complete the problem now.
 
  • #8
Mark44 said:
(-3√3)^(2/3) can also be written as ((-3√3)^2)^(1/3)

Just to make sure, the slope is 1/3?
 
  • #9
I get -1/3.
 

What is implicit differentiation?

Implicit differentiation is a method for finding the derivative of an equation that is not explicitly expressed in terms of one variable. This is useful for finding the slope of a tangent line to a curve at a specific point.

How is implicit differentiation different from regular differentiation?

Regular differentiation involves finding the derivative of a function that is explicitly expressed in terms of one variable. Implicit differentiation, on the other hand, involves finding the derivative of a function that is not explicitly expressed in terms of one variable.

Why is implicit differentiation useful in finding the tangent line?

Implicit differentiation allows us to find the slope of the tangent line at a specific point on a curve without having to solve for one variable in terms of the other. This is particularly useful when the equation is difficult to solve for one variable or when the curve is not a function.

What is the process for finding the tangent line using implicit differentiation?

The first step is to differentiate both sides of the equation with respect to the independent variable. Then, solve for the derivative of the dependent variable. Finally, plug in the x-value of the point of interest to find the slope of the tangent line.

Are there any limitations to using implicit differentiation to find tangent lines?

Implicit differentiation can only find the slope of the tangent line at a specific point on the curve. It cannot provide information about the curve as a whole or about other points on the curve. Additionally, it may be more complicated to use than regular differentiation for certain equations.

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