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Question 53

The sketch shows circle C C\,C with centre P(7.5,5)P(7.5, 5)P(7.5,5). The line l l\,l with equation y=12x\displaystyle y = \frac{1}{2}xy=21​x is a tangent to C C\,C at point Q(8,4)Q(8, 4)Q(8,4).

A sketch of circle C with centre P, touching line l at Q on positive x and y axes.

a.

Find an equation for CCC.

[4]
b.

The line with equation y=12x+k\displaystyle y = \frac{1}{2}x + ky=21​x+k, where k k\,k is a non-zero constant, is also a tangent to CCC. Find the coordinates of the point of contact RRR.

[3]
c.

Hence find the value of kkk.

[2]
Markscheme

Circles Questions

  1. A Level
  2. /Maths
  3. /Circles

292 exam-style questions on Edexcel A Level Maths Circles, covering 6.1 Midpoints and Perpendicular Bisectors, 6.2 Equation of a Circle, 6.3 Intersections of Straight Lines and Circles, 6.4 Use Tangent and Chord Properties, and 6.5 Circles and Triangles. Each one has a worked solution and a mark scheme showing where the marks go.

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