Find cartesian equation from parametric equation

In summary, the conversation discusses the solution for a curve defined by a set of parametric equations. The solution involves rearranging the equations and using trigonometric identities to simplify them. The final solution is expressed in terms of x and y.
  • #1
trollcast
Gold Member
282
13

Homework Statement


A curve is defined by the parametric equations:

$$x=tan(t-1)\ \ \ \ \ \ \ y=cot^2(t+1)$$

Homework Equations


The Attempt at a Solution



I think rearranging the first equation for t gives:

$$t=tan^{-1}(x)+1$$

However that doesn't help me as I don't know how to simplify the equation I'd get if I sub t into the y equation?
 
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  • #2
Do you have to simplify the equation? You found an equation y=f(x).
 
  • #3
mfb said:
Do you have to simplify the equation? You found an equation y=f(x).

I actually just realized that I've misread the equations so I can see how to solve it now.

The equations should be:

$$x=tan(t)-1\qquad y=cot^2(t)+1$$

So the solution would be:

$$tan(t)=x+1$$
$$y=\frac{1}{tan^2(t)}$$
$$y=\frac{1}{(x+1)^2}$$
 
  • #4
trollcast said:
I actually just realized that I've misread the equations so I can see how to solve it now.

The equations should be:

$$x=tan(t)-1\qquad y=cot^2(t)+1$$

So the solution would be:

$$tan(t)=x+1$$
$$y=\frac{1}{tan^2(t)}$$
$$y=\frac{1}{(x+1)^2}$$

What happened to the '+1' in ##y=cot^2(t)+1##?
 
  • #5
Dick said:
What happened to the '+1' in ##y=cot^2(t)+1##?

Oops, so it should be:

$$x=tan(t)-1\qquad y=cot^2(t)+1\\
tan(t)=x+1\\

y - 1=\frac{1}{tan^2(t)}\\
y=\frac{1}{(x+1)^2} +1\\
y=\frac{(x+1)^2+1}{(x+1)^2}$$
 
  • #6
trollcast said:
Oops, so it should be:

$$x=tan(t)-1\qquad y=cot^2(t)+1\\
tan(t)=x+1\\

y - 1=\frac{1}{tan^2(t)}\\
y=\frac{1}{(x+1)^2} +1\\
y=\frac{(x+1)^2+1}{(x+1)^2}$$

Sure.
 

What is a cartesian equation?

A cartesian equation is a mathematical equation that expresses the relationship between two variables using x and y as the independent and dependent variables, respectively.

What is a parametric equation?

A parametric equation is a set of equations that describe the motion of a point in terms of one or more parameters. It is often used to represent curves and surfaces.

How do you convert a parametric equation to a cartesian equation?

To convert a parametric equation to a cartesian equation, you can use the substitution method. Replace the parameters with expressions in terms of x and y, and then eliminate the parameters by solving for x and y.

What are the benefits of using a parametric equation instead of a cartesian equation?

Parametric equations are useful because they can describe complex curves and surfaces that are difficult to represent with cartesian equations. They also allow for more flexibility in defining the shape and motion of an object.

Can any parametric equation be converted to a cartesian equation?

Not all parametric equations have a corresponding cartesian equation. Some curves and surfaces are only defined parametrically and cannot be represented by a single cartesian equation.

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