cricket_freak
New Member
hay guys i was having serious problems with locus questions. can u please explain how to do this question.: Find the equation of the locus of point p(x, y) that moves so that it is always 9 units from the point (-1, -1).
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help please? (1 Viewer)
- Thread starter cricket_freak
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bananasmoothy
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Ok, so basically what you want to find is line that moves around a point - and has the same distance all the way through.cricket_freak said:
So, it's a circle with a radius of 9, and centre (-1, -1). Try to imagine it, or draw it on a bit of paper.
The equation of the locus is the equation of the circle.
SoulSearcher
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the equation of this locus takes the form of the equation of the circle.
i.e (x-h)2 + (y-k)2 = r2, where h and k are the x and y values of the centre of the circle and r is the length of the radius. since the distance from the point (-1,-1) is always nine units, then the radius is 9 and the h and k values of the equation are -1 and -1 respectively
therefore the equation of the locus is
( x + 1 )2 + ( y + 1 )2 = 92
( x + 1 )2 + ( y + 1 )2 = 81
i.e (x-h)2 + (y-k)2 = r2, where h and k are the x and y values of the centre of the circle and r is the length of the radius. since the distance from the point (-1,-1) is always nine units, then the radius is 9 and the h and k values of the equation are -1 and -1 respectively
therefore the equation of the locus is
( x + 1 )2 + ( y + 1 )2 = 92
( x + 1 )2 + ( y + 1 )2 = 81