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How do you rotate a vector by 90 degrees?

Published in Vector Rotation 2 mins read

To rotate a 2D vector by 90 degrees clockwise, you can use a simple trick.

Understanding 90-Degree Vector Rotation

Typically, vector rotation involves matrix mathematics. However, a simpler method exists for rotating 2D vectors 90 degrees clockwise, as referenced from this source (Note: this is a placeholder and the original date and source was provided in the instructions).

The Simple Trick

Here's the process, broken down into two steps:

  1. Negate the X component: Multiply the x-value of your vector by -1.
  2. Swap the X and Y values: Switch the positions of the modified x-value and y-value.

Example

Let's say you have a vector represented as (x, y). Following the steps above:

  • Original Vector: (x, y)
  • Step 1: (-x, y)
  • Step 2: (y, -x)

Therefore, the resulting vector after rotating the original vector 90 degrees clockwise will be (y, -x).

Table Representation

Step Original Vector Transformation Resulting Vector
Initial State (x, y) - (x, y)
Negate X Component (x, y) x = -x (-x, y)
Swap Components (-x, y) Swap x and y (y, -x)

Practical Application

  • Consider a vector (2, 3).
  • Following the steps, we first negate x, making it (-2, 3).
  • Then, we swap x and y values, getting (3, -2).
  • So the original vector (2,3) rotated 90 degrees clockwise becomes (3,-2).

Summary

Rotating a 2D vector by 90 degrees clockwise is achieved by negating the x-component and then swapping the x and y values. This is a simplified approach that avoids complex matrix calculations.

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