Locating a Moving Point P: x+y=9

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SUMMARY

The locus of the moving point P, defined by the condition that the length of the tangent from P to the circle x²+y²=16 equals the distance from P to the point (8,8), is established as the straight line x+y=9. This conclusion is derived by setting the coordinates of point P as (a,b) and equating the tangent length to the distance from (8,8). The solution involves applying the distance formula and properties of tangents to circles.

PREREQUISITES
  • Understanding of circle equations, specifically x²+y²=16.
  • Knowledge of the distance formula in coordinate geometry.
  • Familiarity with the concept of tangents to circles.
  • Basic algebraic manipulation skills to solve equations.
NEXT STEPS
  • Study the properties of tangents to circles in coordinate geometry.
  • Learn how to derive the equation of a locus from geometric conditions.
  • Explore the distance formula and its applications in geometry.
  • Practice solving problems involving loci and geometric constraints.
USEFUL FOR

Students studying coordinate geometry, mathematics educators, and anyone interested in understanding the geometric properties of loci and tangents in circles.

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Homework Statement



A moving point P is such that the length of the tangent from P to the circle x2+y2=16 is equal to the distance of P from point (8,8). Show that the locus of P is the straight line x+y=9.

Homework Equations





The Attempt at a Solution



I sketched a graph for this, but it doesn't seems to help me a lot in solving this question. Can anyone give me some hints? Thanks...
 
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Well, let the point P be (a,b). What is the length of the tangent to the circle? What is its distance from (8,8)? Equate the two.
 

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