Let be the circle and be the locus of the point of intersection of a pair of tangents to with the angle between the two tangents equal to . Then, the point at which touches the line is
Let be the circle and be the locus of the point of intersection of a pair of tangents to with the angle between the two tangents equal to . Then, the point at which touches the line is
Solution
Given:
The standard form of a circle is , where is the center and is the radius.
For x: (add and subtract 4)
For y: (add and subtract 9)
Center and Radius
When two tangents are drawn from an external point P to a circle, the tangents have equal length and the angle between the center-to-point line and each tangent is the same.
If the angle between the two tangents is , then each tangent makes an angle of with the line joining the external point to the center.
In the right triangle formed by:
A point of tangency
C center of circle
P external point
We have:
(radius perpendicular to tangent)
(half of the angle between tangents)
(radius)
Using trigonometry in right triangle ACP:
Since :
Therefore:
The locus L consists of all points P that are at distance 8 from the center .
Locus equation:
We substitute into the locus equation:
The point where L touches the line is .
The point is exactly 8 units away from the center , confirming our geometric analysis. From this point, tangents drawn to the circle will indeed make a angle with each other.
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CAT 2020 Slot 1