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    This question is from Edexcel, June 2010, C2
    The circle C has centre A(2,1) and passes through the point B(10, 7) .

    (a) Find an equation for C.

    The line L1 is the tangent to C at the point B.

    (b) Find an equation for L1

    The line L2 is parallel to L1 and passes through the mid-point of AB.

    Given that intersects C at the points P and Q,

    (c) Find the length of PQ, giving your answer in its simplest surd form.
    I've done a and b but I don't understand how to get c.
    Any help on explaining how to get c would be very much appreciated, thanks
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    Never mind, I've figured it out
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    You've got the equation of L2: Same gradient as L1, and it passes through the midpoint of AB which you can find, plug it in to y-y1=m(x-x1). You know that L2 intersects the circle at 2 points (P&Q), you should be able to see what to do from there.
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    In case anyone googled this to find out how to do part c), here is how I did it:
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    Hope that helps
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    Turns out I didn't read the question right.. Thanks for the help though
 
 
 
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