parametric question (1 Viewer)

[AGB]

can sum1 please help me?? you will prob find this v. easy, but i just keep going round in circles....

elimate the parameter and then find the cartesian equation when:

x = t + 1/t
y = t^2 + 1/t^2

thanx in advance

 

[Rahul]

hmmm tricky one...

x = t + 1/t
dx/dt = ln(t)

y = t^2 + 1/t^2
dy/dt = 2t - 2/t
=(2t^2 - 2)/t^2

dy/dx = dy/dt / dx/dt
= (2t^2 - 2)/t^2.ln(t)

mmm...i have no idea really
i'll leave this up, just in case it helps.

 

[AGB]

i just got it (after half an hour of trying....)

x = (t + 1/t)
y = t^2 + 1/t^2
= (t + 1/t)^2 - 2

therefore y = x^2 - 2

yay!! haha

 

[Rahul]

well done

i should have known that, coz i've done similar q's before *dumbass* i even thought of that identity

 

[kimmeh]

rahul.. why bother differentiating it?

 

[Rahul]

bah, you are supposed to use it when dealing with chords. i dont know what i was thinking.

havent done parametric for a while and that was one of the things i vaguely remembered from doing it.

its something to remember, but then again you have to use it at the right time.

 

[Rand]

That was a piss easy Question dudes,


coz Ive seen it before