IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: RomanianGuy on February 08, 2011, 04:20:13 pm

Title: Edexcel Coordinates Geometry!! Please help!! :(
Post by: RomanianGuy on February 08, 2011, 04:20:13 pm

Hey!

I find this topic difficult for a reason :/

I've got a question which says:

"The circle C has centre (-3,2) and passes through the point (2,1)

a) find an equation for C
b) show that the point with co-ordinates (-4,7) lies of C

c) Find an equation for the tangent to C at the point (-4,7). Give your answer  in the form ax+by+c = 0, where a, b and c are integers.


PLEASE HELP GUYS!!!! IT DROVE ME MAD WHILE TRYIN TO ANSWER IT!

Title: Re: Edexcel Coordinates Geometry!! Please help!! :(
Post by: iluvme on February 08, 2011, 06:05:29 pm

a) First find the gradient of the line, C using both coordinates you've been provided with. The equation would be, (y₂-y₁)/(x₂-x₁)
   
    Then use the equation, y₂-y₁=m(x₂-x₁) where m is the gradient.


b)Then substitute either the x value or y value from (-4,7) in your equation above, and check if you've obtained your corresponding x or y value, depending on what you substituted. If your equation was right, you'd get the corresponding values.

c) The equation of the tangent and line C would be the same, so by using the above method to find the equation, you'd be able to find the equation.

:)