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Cesar Del rio
Cesar Del rio

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#1 - Points of reflection (8 kyu) Codewars Kata

#1 - Points of reflection (8 kyu)

Instructions:
"Point reflection" or "point symmetry" is a basic concept in geometry where a given point, P, at a given position relative to a mid-point, Q has a corresponding point, P1, which is the same distance from Q but in the opposite direction.

Task
Given two points P and Q, output the symmetric point of point P about Q. Each argument is a two-element array of integers representing the point's X and Y coordinates. Output should be in the same format, giving the X and Y coordinates of point P1. You do not have to validate the input.

My notes:

Image description

My solution:

function symmetricPoint(p, q) {
  return [2*q[0]-p[0], 2*q[1]-p[1] ]
}
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Explanation
I found the formula for getting the P1 coordinate, the formula is P1(2Qx - Px, 2Qy - Py), then I just passed this formula with the array index positions and returned the result as an array

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