when preforming one translation after another, does the order matter? why or why not?

1 answer

Yes, the order of translations does matter because translations are not commutative operations. In geometric transformations, if you perform one translation followed by another, the final position will depend on the order in which those translations are applied.

For example, consider two translations: \( T_1 \) that moves a point \( (x, y) \) by a vector \( (a, b) \) and \( T_2 \) that moves the point by another vector \( (c, d) \).

  1. If you first apply \( T_1 \) and then \( T_2 \), the point moves to: \[ (x + a, y + b) \quad \text{(after } T_1\text{)} \] then to: \[ (x + a + c, y + b + d) \quad \text{(after } T_2\text{)} \]

  2. If you first apply \( T_2 \) and then \( T_1 \), the point moves to: \[ (x + c, y + d) \quad \text{(after } T_2\text{)} \] then to: \[ (x + c + a, y + d + b) \quad \text{(after } T_1\text{)} \]

In both cases, you need to add the respective vectors, resulting in:

  • \( T_1 \) followed by \( T_2 \): \( (x + a + c, y + b + d) \)
  • \( T_2 \) followed by \( T_1 \): \( (x + c + a, y + d + b) \)

Since vector addition is commutative, ultimately in terms of position, the final coordinates will be the same regardless of the order of translations. Thus, for translations, while the individual operations themselves are not commutative in the sense of "visually" observing the steps involved, the resultant endpoint after performing two translations will yield the same final coordinate.

However, in contexts where translations are applied along other transformations (like rotations or reflections), the order can drastically affect the final result, since those transformations interact differently with the translation process. In summary, for pure translations, the final position will be invariant to the order, but be cautious in context with other transformations.