You are Here: Home >< Maths

# parametric equations help a2 watch

1. Obtain a cartesian equation for this pair of parametric equations: x=cot(theta), y=2cosec(theta). I have no idea how to go about this as Im used to x and y being in terms of cos and sin, respectively. What, at least, would be the first step?
2. (Original post by itlstallion69)
Obtain a parametric equation for this pair of parametric equations: x=cot(theta), y=cosec(theta). I have no idea how to go about this as Im used to x and y being in terms of cos and sin, respectively. What, at least, would be the first step?
You wish to obtain the equation of the curve entirely in terms of . Since you got trig in there, a good start is to have a think what identities link and
3. (Original post by RDKGames)
Do you mean obtain the Cartesian equation...?

In which case, you wish to obtain the equation of the curve entirely in terms of . Since you got trig in there, a good start is to have a think what identities link and
I know that cot^(2)x =cosec^(2)x -1, but I cant see how that would apply in getting the cartesian equations
4. (Original post by itlstallion69)
I know that cot^(2)x =cosec^(2)x -1, but I cant see how that would apply in getting the cartesian equations
That's right. So then you want to get and from what you got.

Note that if then . So in the identity you can replace by . Repeat similarly for
5. (Original post by RDKGames)
That's right. So then you want to get and from what you got.

Note that if then . So in the identity you can replace by . Repeat similarly for
Following that, my answer was 4x^2 +y^2-4=0, but the book gives 4x^2 -y^2 +4=0
6. (Original post by itlstallion69)
Following that, my answer was 4x^2 +y^2-4=0, but the book gives 4x^2 -y^2 +4=0
Didnt notice you changes cosec to 2cosec.

So then, anyway, and

Hence and

Subbing these into the identity yields which arranges to their given answer.

Not sure where you're error lies without you showing your working out.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 28, 2018
Today on TSR

### University open days

• Southampton Solent University
Sun, 18 Nov '18
Wed, 21 Nov '18
• Buckinghamshire New University
Wed, 21 Nov '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams