Please help me with this C4 question

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ClarissaEmile
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I'm a retake student and I can't do trig )) please help

Can someone give me a step:
Question: find the Cartesian equation of the curve with parametric equations x = cos t + 2 y = 4sec t
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Sir Cumference
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(Original post by ClarissaEmile)
I'm a retake student and I can't do trig )) please help

Can someone give me a step:
Question: find the Cartesian equation of the curve with parametric equations x = cos t + 2 y = 4sec t
First change each equation so that the trig ratio is the subject of the equation. Post your working if you get stuck.
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ClarissaEmile
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That's what I got initially and it's wrong ://
cantrelate
Last edited by ClarissaEmile; 1 year ago
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ClarissaEmile
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(Original post by Notnek)
First change each equation so that the trig ratio is the subject of the equation. Post your working if you get stuck.
I did that I'm just not sure which identities to use
I tried 1/cos t = sec t
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Sir Cumference
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What you've done is correct. Maybe you need to rearrange it to get it into the form given in the answer? What was the answer given?
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cantrelate
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That’s so strange. Where is the question from? What paper/book?
(Original post by ClarissaEmile)
That's what I got initially and it's wrong ://
cantrelate
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mnot
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(Original post by ClarissaEmile)
I'm a retake student and I can't do trig )) please help

Can someone give me a step:
Question: find the Cartesian equation of the curve with parametric equations x = cos t + 2 y = 4sec t
multiple approaches available, make both equations equal to each other (in terms of t) then generate a new form or use substitution ie find t in 1 equation and sub into the 2nd form. This should be very easy...
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ClarissaEmile
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(Original post by cantrelate)
That’s so strange. Where is the question from? What paper/book?
(Original post by Notnek)
What you've done is correct. Maybe you need to rearrange it to get it into the form given in the answer? What was the answer given?
The answer is y = 4/x-2
Am I just being dumb and haven't rearranged it??

It's from an edexcel textbook
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Sir Cumference
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cantrelate please don't post solutions - it's against the rules of the maths forum. I thought you were the OP when I replied.
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Sir Cumference
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(Original post by ClarissaEmile)
The answer is y = 4/x-2
Am I just being dumb and haven't rearranged it??

It's from an edexcel textbook
I think you just need to rearrange it. If you're still stuck please post your working.
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ClarissaEmile
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(Original post by ClarissaEmile)
The answer is y = 4/x-2
Am I just being dumb and haven't rearranged it??

It's from an edexcel textbook
Lmao wow I just realised how easy that rearrangement was sorry I'm half asleep :')

Notnek
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Thank you xx
Last edited by ClarissaEmile; 1 year ago
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cantrelate
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(Original post by ClarissaEmile)
The answer is y = 4/x-2
Am I just being dumb and haven't rearranged it??

It's from an edexcel textbook
Oh haha they just rearranged it! Multiply the last line by y to get xy= 4+2y then take the 2y to the other side and factorise out y. Bring the bracket to the rhs and you get that equation!
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timif1
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(Original post by Notnek)
I think you just need to rearrange it. If you're still stuck please post your working.
Do you think OP would still get awarded full marks? Unless they explicitly state (as a function of x or y) or rearrange for x or y surely you should still get the marks

Thanks
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Sir Cumference
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(Original post by timif1)
Do you think OP would still get awarded full marks? Unless they explicitly state (as a function of x or y) or rearrange for x or y surely you should still get the marks

Thanks
If the question was written exactly as it is the first post of this thread then any correct cartesian equation would get the marks. An exam question would probably specify the form e.g. y=f(x).
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Vinny C
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(Original post by Notnek)
First change each equation so that the trig ratio is the subject of the equation. Post your working if you get stuck.
Damn... you are good.
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Vinny C
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(Original post by Notnek)
If the question was written exactly as it is the first post of this thread then any correct cartesian equation would get the marks. An exam question would probably specify the form e.g. y=f(x).
You are very good... done this before?
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