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Core/Pure 1 Homework on Circles watch

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    I've got this homework and I am totally confused because the questions are nothing like we did in class. I've done over 2/3, but I'm completely lost on some of them.

    Here's one:

    - The y-axis is a tangent to the circle which crosses the x-axis at (8,0) and (18,0)

    (i) Find the radius of this circle and co-ords of its centre.

    (ii) Find the equation of the circle in form x2 + y2 + px + gy + r = 0
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    (Original post by and87)
    I've got this homework and I am totally confused because the questions are nothing like we did in class. I've done over 2/3, but I'm completely lost on some of them.

    Here's one:

    - The y-axis is a tangent to the circle which crosses the x-axis at (8,0) and (18,0)

    (i) Find the radius of this circle and co-ords of its centre.

    (ii) Find the equation of the circle in form x2 + y2 + px + gy + r = 0
    is there any point doing this seeing as the exam has been?
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    Every point seeing as my exam for C1 is in June.
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    (Original post by and87)
    Every point seeing as my exam for C1 is in June.
    Didnt you have any core 1/core 2 modules this time round?
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    No. I've got both core exams in May/June period. I had discrete yesterday.
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    This is quite a guess as i am quite pissed!

    I think the radus will be 13, (the mid-point between 8 and 18 is 13, and as the y-axis is the tangent, 13 will also be the x-value for the mid point)

    Im thinking about it but thats al i have, but ill try when sober!
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    (Original post by DOJO)
    Didnt you have any core 1/core 2 modules this time round?
    My school doesnt believe in Jan modules so I take c1-4, m1 + s1 in the Summer! Should be entertaining...
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    (Original post by and87)
    Every point seeing as my exam for C1 is in June.
    Oh, sorry i was completely oblivious to the fact that some people are having them in June. Sorry, i only wish mine would have been then!
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    (Original post by and87)
    I've got this homework and I am totally confused because the questions are nothing like we did in class. I've done over 2/3, but I'm completely lost on some of them.

    Here's one:

    - The y-axis is a tangent to the circle which crosses the x-axis at (8,0) and (18,0)

    (i) Find the radius of this circle and co-ords of its centre.

    (ii) Find the equation of the circle in form x2 + y2 + px + gy + r = 0
    Draw the circle, touching y axis and crossing x axis at given points.

    draw x=13. This bisects AB where A is 8,0 and B is 18,0

    You can now see the centre must lie on x=13, and so the radius is 13, since the distance between the point where the circle touches the y axis and x=13 is 13.

    You have a couple of nice 5,12,13 triangles between A,B, and O. (the centre)
    which allow you to locate the centre. Then build your equation.

    Aitch
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    Isnt this circle stuff in C2?
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    (Original post by sash37uk)
    Isnt this circle stuff in C2?
    It was in P3 when I did it!

    Aitch
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    (Original post by Aitch)
    It was in P3 when I did it!

    Aitch
    Yeah, same. But they've put it in C2 now.
 
 
 
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