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How does scalar multiplication affect a vector's coordinates and direction?

Scalar multiplication scales each coordinate of the vector by the scalar value. If the scalar is positive, the direction of a nonzero vector is preserved. If the scalar is negative, the direction is reversed. If the scalar is zero, the result is the zero vector, which has no direction.

Conditions

  • k is a real scalar.
  • The component formula applies to every real scalar.
  • Direction preservation/reversal applies to nonzero vectors.

Reasoning, step by step

  1. Multiply the first coordinate by the scalar k.
  2. Multiply the second coordinate by the scalar k.
  3. Observe the new magnitude and direction based on the sign of k.

Example

2×[20]=[40]2 \times \begin{bmatrix} 2 \\ 0 \end{bmatrix} = \begin{bmatrix} 4 \\ 0 \end{bmatrix}. The direction remains the same because 2 is positive.

Common misconceptions

  • Thinking that scalar multiplication changes the direction for any nonzero scalar.
  • Believing that the zero vector has a direction.
  • Adding the scalar to the coordinates instead of multiplying.

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