What does the magnitude of the cross product a × b represent?

The magnitude of the cross product of two vectors a and b, denoted as |a × b|, is a measure of the area of the parallelogram formed by these two vectors. This geometric interpretation is very useful in understanding the relationship between the vectors in three-dimensional space.

The formula to calculate the magnitude of the cross product is given by:

|a × b| = |a| * |b| * sin(θ)

Where:

  • |a| is the magnitude (length) of vector a,
  • |b| is the magnitude (length) of vector b, and
  • θ is the angle between the two vectors.

To further explain, the magnitude of the cross product depends on both the lengths of the vectors and the sine of the angle between their directions. If the vectors are parallel, the angle θ is 0°, and hence sin(0°) = 0, resulting in a cross product magnitude of zero. This means that there is no area and the vectors do not span a surface. Conversely, when the vectors are perpendicular (90°), sin(90°) = 1, yielding the maximum area of the parallelogram formed by the two vectors.

In summary, the magnitude of the cross product is not just a number; it provides valuable insight into the spatial relationship between two vectors, indicating both their lengths and the angle at which they intersect.

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