The locus of the mid-points of the chords of x2 + y2 + 4x - 6y - 12 = ...
The locus of the mid-points of the chords of x2 + y2 + 4x - 6y - 12 = ...
To find the locus of the mid-points of the chords that subtend an angle of 90 degrees, we need to find the equation of the circle passing through the endpoints of these chords.
First, let's rewrite the given equation in the standard form of a circle:
x^2 + y^2 + 4x - 6y - 12 = 0
Completing the square for x and y terms, we have:
(x^2 + 4x) + (y^2 - 6y) - 12 = 0
(x^2 + 4x + 4) + (y^2 - 6y + 9) - 12 = 4 + 9
(x + 2)^2 + (y - 3)^2 = 17
So the given equation represents a circle centered at (-2, 3) with a radius of √17.
Now, let's find the endpoints of the chords that subtend a 90-degree angle. Since the angle is right, the chords will be diameters of the circle.
The diameter of a circle passes through its center, so the endpoints of the diameter will be (-2, 3) and another point on the circle.
To find another point on the circle, we can use the equation of the circle and choose a value for x that satisfies it. Let's choose x = 0:
(x + 2)^2 + (y - 3)^2 = 17
(0 + 2)^2 + (y - 3)^2 = 17
4 + (y - 3)^2 = 17
(y - 3)^2 = 17 - 4
(y - 3)^2 = 13
y - 3 = ±√13
y = 3 ± √13
The two points on the circle are (0, 3 + √13) and (0, 3 - √13). The midpoint of these two points will be the center of the chord, which is also the center of the circle (-2, 3).
Therefore, the locus of the mid-points of the chords that subtend an angle of 90 degrees is the point (-2, 3).