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With respect to right-handed Cartesian coordinates, let \(a-[1,2,0], b-[3,-4,0], c-[3,5,2], d=[6,2,-3]\) Showing details, find: $$a \cdot(b \times c),(a \times b) \cdot c$$

Short Answer

Expert verified
Both results are -20.

Step by step solution

01

Understand the given points and vectors

We have four points or vectors: \(a = [1, 2, 0]\), \(b = [3, -4, 0]\), \(c = [3, 5, 2]\), \(d = [6, 2, -3]\). The exercise asks us to find two different expressions involving dot and cross products.
02

Calculate the Cross Product \(b \times c\)

To find \(b \times c\), use the following determinant formula for a cross product:\[b \times c = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \ 3 & -4 & 0 \ 3 & 5 & 2 \end{vmatrix}\]Calculate it by performing the determinant expansion:- \( \mathbf{i}( (-4)(2) - (0)(5) ) = -8\mathbf{i} \)- \(-\mathbf{j}(3 \times 2 - 0 \times 3) = -6\mathbf{j} \)- \(\mathbf{k}(3 \times 5 - (-4) \times 3) = 27\mathbf{k} \)Thus, \(b \times c = [-8, -6, 27]\).
03

Calculate the Dot Product \(a \cdot (b \times c)\)

Now, use the result from Step 2 to calculate \(a \cdot (b \times c)\). We have \(a = [1, 2, 0]\) and \(b \times c = [-8, -6, 27]\).The dot product is given by:\[a \cdot (b \times c) = 1 \cdot (-8) + 2 \cdot (-6) + 0 \cdot 27 = -8 - 12 + 0 = -20\]Thus, \(a \cdot (b \times c) = -20\).
04

Calculate the Cross Product \(a \times b\)

Now calculate \(a \times b\):\[a \times b = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \ 1 & 2 & 0 \ 3 & -4 & 0 \end{vmatrix}\]Using determinant expansion:- \( \mathbf{i}(2 \times 0 - 0 \times (-4)) = 0\mathbf{i} \)- \(-\mathbf{j}(1 \times 0 - 0 \times 3) = 0\mathbf{j} \)- \(\mathbf{k}(1 \times (-4) - 2 \times 3) = -10\mathbf{k} \)So, \(a \times b = [0, 0, -10]\).
05

Calculate the Dot Product \((a \times b) \cdot c\)

Finally, calculate \((a \times b) \cdot c\) using the vectors from Step 4 and the given \(c = [3, 5, 2]\).\[(a \times b) \cdot c = [0, 0, -10] \cdot [3, 5, 2] = 0 \cdot 3 + 0 \cdot 5 + (-10) \cdot 2 = 0 + 0 - 20 = -20\]Therefore, \((a \times b) \cdot c = -20\).

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Key Concepts

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

Dot Product
The dot product, often called the scalar product, is a way to multiply two vectors that results in a single number, or scalar. This operation is very useful in physics and engineering as it helps to find how much of one vector goes in the direction of another. Mathematically, for two vectors \( \mathbf{a} = [a_1, a_2, a_3] \) and \( \mathbf{b} = [b_1, b_2, b_3] \), the dot product is calculated as:\[ \mathbf{a} \cdot \mathbf{b} = a_1b_1 + a_2b_2 + a_3b_3 \]
  • Helps to find the angle between two vectors.
  • Results in a scalar value.
  • Is zero if vectors are perpendicular.
In the exercise, we used the dot product to find \(a \cdot (b \times c)\) and \((a \times b) \cdot c\). Each case results in -20 as the computed scalar."},{"concept_headline":"Cross Product","text":"The cross product, or vector product, of two vectors results in a third vector that is perpendicular to the plane containing the initial vectors. This is vital in calculating torque and rotational movements. For vectors \( \mathbf{a} = [a_1, a_2, a_3] \) and \( \mathbf{b} = [b_1, b_2, b_3] \), the cross product is represented and calculated using a determinant:\[ \mathbf{a} \times \mathbf{b} = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \ a_1 & a_2 & a_3 \ b_1 & b_2 & b_3 \end{vmatrix} \]In essence:- The direction of the resulting vector is given by the right-hand rule.- The magnitude can be found by \( |\mathbf{a} \times \mathbf{b}| = |\mathbf{a}| |\mathbf{b}| \sin(\theta) \) where \( \theta \) is the angle between \( \mathbf{a} \) and \( \mathbf{b} \).We used this in our solution to compute \(b \times c\) and \(a \times b\). The specific values were computed based on carefully handling the determinant to obtain the vectors."},{"concept_headline":"Cartesian Coordinates","text":"Cartesian coordinates are a fundamental mathematical system used to describe the position of a point in space with numbers, using three perpendicular axes: \(x\), \(y\), and \(z\). This system supports computations in vector calculus, such as dot and cross products, by providing a framework for vectors.
  • Each point or vector is described as \([x, y, z]\).
  • Allows easy visualization and calculation in three-dimensional space.
  • Widely used in physics, engineering, and computer graphics.
In our exercise, all vectors are given in Cartesian coordinates making the calculations straightforward. The coordinates facilitate easily locating vectors in the 3D space and performing operations like the dot and cross product without needing conversion to another coordinate system."}]}]}plugins. Omega_component:MiniArticle _notifications:Assistant _assistentelementscomponentsSECTION: 0_A_DEFINITION: [
Dot Product
The dot product, often called the scalar product, is a way to multiply two vectors that results in a single number, or scalar. This operation is very useful in physics and engineering as it helps to find how much of one vector goes in the direction of another. Mathematically, for two vectors \( \mathbf{a} = [a_1, a_2, a_3] \) and \( \mathbf{b} = [b_1, b_2, b_3] \), the dot product is calculated as:\[ \mathbf{a} \cdot \mathbf{b} = a_1b_1 + a_2b_2 + a_3b_3 \]
  • Helps to find the angle between two vectors.
  • Results in a scalar value.
  • Is zero if vectors are perpendicular.
In the exercise, we used the dot product to find \(a \cdot (b \times c)\) and \((a \times b) \cdot c\). Each case results in -20 as the computed scalar.
Cross Product
The cross product, or vector product, of two vectors results in a third vector that is perpendicular to the plane containing the initial vectors. This is vital in calculating torque and rotational movements. For vectors \( \mathbf{a} = [a_1, a_2, a_3] \) and \( \mathbf{b} = [b_1, b_2, b_3] \), the cross product is represented and calculated using a determinant:\[ \mathbf{a} \times \mathbf{b} = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \ a_1 & a_2 & a_3 \ b_1 & b_2 & b_3 \end{vmatrix} \]In essence:- The direction of the resulting vector is given by the right-hand rule.- The magnitude can be found by \( |\mathbf{a} \times \mathbf{b}| = |\mathbf{a}| |\mathbf{b}| \sin(\theta) \) where \( \theta \) is the angle between \( \mathbf{a} \) and \( \mathbf{b} \).We used this in our solution to compute \(b \times c\) and \(a \times b\). The specific values were computed based on carefully handling the determinant to obtain the vectors.
Cartesian Coordinates
Cartesian coordinates are a fundamental mathematical system used to describe the position of a point in space with numbers, using three perpendicular axes: \(x\), \(y\), and \(z\). This system supports computations in vector calculus, such as dot and cross products, by providing a framework for vectors.
  • Each point or vector is described as \([x, y, z]\).
  • Allows easy visualization and calculation in three-dimensional space.
  • Widely used in physics, engineering, and computer graphics.
In our exercise, all vectors are given in Cartesian coordinates making the calculations straightforward. The coordinates facilitate easily locating vectors in the 3D space and performing operations like the dot and cross product without needing conversion to another coordinate system.

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