Answer:
Step-by-step explanation:
Rotation 180° (in either direction) about the origin causes each coordinate to have its sign changed. Effectively, the coordinate matrix is multiplied by -1.
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<em>Additional comment</em>
This is equivalent to reflection across the origin.
I think it is :.
But...not really sure
The perpendicular distance between the chord and the center of the circle forms a right triangle with the chord and the radius. Using trig:
sin 30° = x / (D/2)
sin 30° = 2x / D
1/2 = 2x / D
x = D/4
Assuming he met them at the same time, he said Hi once.