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If \(\mathbf{A}\) and \(\mathbf{B}\) are the diagonals of a parallelogram, find a vector formula for the area of the parallelogram.

Short Answer

Expert verified
\(\frac{1}{2}\|\mathbf{A} \times \mathbf{B}\|\)

Step by step solution

01

Understand the relationship between diagonals and area

In a parallelogram, the area can be found using the cross product of two adjacent sides. However, given the diagonals \(\mathbf{A}\) and \(\mathbf{B}\), another approach involves using these diagonals.
02

Express sides in terms of diagonals

Let the vertices of the parallelogram be \(\mathbf{O}\), \(\mathbf{P}\), \(\mathbf{Q}\), and \(\mathbf{R}\) such that \(\mathbf{A} = \mathbf{OP} + \mathbf{OR}\) and \(\mathbf{B} = \mathbf{OQ} + \mathbf{OR}\). The sides of the parallelogram formed by \(\mathbf{P}\) and \(\mathbf{Q}\), for example, can be expressed as \(\mathbf{a}\) and \(\mathbf{b}\).
03

Use vector properties to find area

The area of the parallelogram is mathematically \(\|\mathbf{a} \times \mathbf{b}\|\). Since \(\mathbf{a}\) and \(\mathbf{b}\) can be represented as a half-sum of diagonals, we modify it to \(\|\frac{1}{2}(\mathbf{A} \times \mathbf{B})\|\).
04

Simplify the expression

Finally, the area of the parallelogram can be simplified to \(\frac{1}{2}\|\mathbf{A} \times \mathbf{B}\|\). This is derived from the fact that diagonals of a parallelogram bisect each other and split it into two congruent triangles.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cross Product
The cross product is a powerful tool in vector calculus, used to find a vector perpendicular to two given vectors. If you have vectors \(\textbf{u}\) and \(\textbf{v}\), their cross product, denoted \(\textbf{u} \times \textbf{v}\), is a vector perpendicular to both. Mathematically, the cross product is given by the determinant formula:

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