Easy Parametrics Q (2 Viewers)

[kaz1]

7. 2x-y+4=0

x=t-2 y=2t

8. x²+y²=9

x=t y=sqareroot(9-t²)

i think...
u can just sub in random stuff

Isn't the parametric equation for a circle x=rcosθ and y=rsinθ
so it would be x=3cosθ and y=3sinθ but I'm not really sure.

 

[azureus88]

there could be more than one answer when you convert cartesian equation to parametric.

the easiest way is to either make something the subject or use trig identities.
for 7, you could even have y=2t-4 and x=t

 

[Fortian09]

u sure u just sub randoms? coz it doesnt seem right like i dont know the steps involved

 

[jet]

Yeah for a circle x^2 + y^2 = r^2
The parametrics are x=rcost, y=rsint

You can work this out using the triangle created by the x-axis, the radius and the height to the point. The parameter, t (or theta) will be the angle between the radius and the x-axis. (The length of the triangle on the x-axis is the projection of the radius on the x-axis)

 

[Timothy.Siu]

Isn't the parametric equation for a circle x=rcosθ and y=rsinθ
so it would be x=3cosθ and y=3sinθ but I'm not really sure.

yeah i guess so, that wud make more sense, but u can really do anytihng as long as it works right?

 

[Fortian09]

does anyone mind put all the parametric equations general forms plz?
that wud be a great help to everyone having trouble (probs only me)

 

[azureus88]

What do u mean by general form? General form for parmetric equations is x=.... and y=.... where x and y are in terms of a parameter t right?

 

[Fortian09]

yer that, it would be great thanks