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# help Watch

No! I am not winding you up! dont worry

But yea, I know that... but where do I get these numbers?!! there are no coordinates in the question or anything?? Eugh, i give up on this, ill move onto the next question on the book...
Can you find a relationship between (1,1) ; (2,2) ; (3,3) ... (n,n)?
2. (Original post by Noble.)

For the circle to 'touch' each axis we must have that the centre point of the circle is of the form where

Since we also have that lies on the line we must have but we also know that , so gives the centre of the circle being now the radius is also obvious.
I understand it now, that was more helpful than all the other posts combined.

Thanks
I understand it now, that was more helpful than all the other posts combined.

Thanks
No it wasn't. You think it was helpful because I told you the answer, you need to learn to think for yourself - you're going to be royally screwed in AS Maths exams in all honesty.
4. (Original post by Noble.)

For the circle to 'touch' each axis we must have that the centre point of the circle is of the form where

Since we also have that lies on the line we must have but we also know that , so gives the centre of the circle being now the radius is also obvious.
why are we allowed to set b equal to 3a-4?
why are we allowed to set b equal to 3a-4?
Because it lies on the line y=3x-4
6. (Original post by Noble.)
No it wasn't. You think it was helpful because I told you the answer, you need to learn to think for yourself - you're going to be royally screwed in AS Maths exams in all honesty.
But I now understand it as you showed me how to arrive at the answer, I have thought about it
7. (Original post by Noble.)
Because it lies on the line y=3x-4
I think he means why do we have the x co ordinate = to the y coordinate?

Is the centre the origin?
8. (Original post by joostan)
Can you find a relationship between (1,1) ; (2,2) ; (3,3) ... (n,n)?
yep, the x and y coordinates are equal distance from the axis
yep, the x and y coordinates are equal distance from the axis
OK so can you see how this is a requirement for the circle? The centre must be equidistant from the x-axis and the y-axis?
But I now understand it as you showed me how to arrive at the answer, I have thought about it
Yes, but this was for a specific case, unless you get the identical question, you're probably not going to know how to do it. How about this, it's essentially the exact same question:

"A circle touches the negative y-axis and the negative x-axis and it's centre lies on the line y=5x+7. What is the equation of the circle?"
11. (Original post by Noble.)
Yes, but this was for a specific case, unless you get the identical question, you're probably not going to know how to do it. How about this, it's essentially the exact same question:

"A circle touches the negative y-axis and the negative x-axis and it's centre lies on the line y=5x+7. What is the equation of the circle?"
b=5a+7 but since they are equal distance form the axis then a=5a+7 therefore a=-7/4 and b=-7/4

job done
b=5a+7 but since they are equal distance form the axis then a=5a+7 therefore a=-7/4 and b=-7/4

job done
Where's the equation of the circle?
13. (Original post by Noble.)
Where's the equation of the circle?
My turn for questions...

Why is it an equal distance from both sets of axis? (x=y)

The centre isn't the origin?
14. (Original post by Noble.)
Where's the equation of the circle?
sorry forgot that part :P

It would be (x+7/4)^2 + (y+7/4)^2 = 49/16 ??
15. (Original post by L'Evil Fish)
My turn for questions...

Why is it an equal distance from both sets of axis? (x=y)

The centre isn't the origin?
Because it just touches both axes, so the centre point must satisfy x=y, otherwise the circle would 'overhang' one of the axes, or not touch it.
16. (Original post by Noble.)
Because it just touches both axes, so the centre point must satisfy x=y, otherwise the circle would 'overhang' one of the axes, or not touch it.
oh, it lies on them?

I thought it just crossed over it like one tiny part of it
17. (Original post by L'Evil Fish)
oh, it lies on them?

I thought it just crossed over it like one tiny part of it
Generally when it says 'touches' it means just at one point.
18. (Original post by Noble.)
Generally when it says 'touches' it means just at one point.
Was the equation right?

do you mind asking me some more c2 circle questions? I just find I try a lot harder in them if I am doing them for someone else... only if you don't mind
19. (Original post by Noble.)
Generally when it says 'touches' it means just at one point.
That makes a lot more sense now sorry about that
Was the equation right?

do you mind asking me some more c2 circle questions? I just find I try a lot harder in them if I am doing them for someone else... only if you don't mind
Given that the radius is a solution to and the point lies on the circle and given that all points on the circle are positive, that is and what conditions must we put on the centre of the circle to ensure a circle satisfies all these things?

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