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The scalar vecA.(vecB+vecC)xx(vecA+vecB+...

The scalar `vecA.(vecB+vecC)xx(vecA+vecB+vecC)` equals (A) 0 (B) `[vecA vecB vecC]+[vecB vecC vecA]` (C) `[vecA vecB vecC]` (D) none of these

A

0

B

`[vecA vecB vecC]+ [vecB vecC vecA] `

C

`[vecA vecB vecC]`

D

none of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the expression \( \vec{A} \cdot (\vec{B} + \vec{C}) \times (\vec{A} + \vec{B} + \vec{C}) \). ### Step 1: Expand the expression We start by expanding the expression using the distributive property of the dot product and the cross product. \[ \vec{A} \cdot (\vec{B} + \vec{C}) \times (\vec{A} + \vec{B} + \vec{C}) = \vec{A} \cdot \left( \vec{B} \times (\vec{A} + \vec{B} + \vec{C}) + \vec{C} \times (\vec{A} + \vec{B} + \vec{C}) \right) \] ### Step 2: Apply the cross product Now we can apply the cross product to each term separately: \[ = \vec{A} \cdot \left( \vec{B} \times \vec{A} + \vec{B} \times \vec{B} + \vec{B} \times \vec{C} + \vec{C} \times \vec{A} + \vec{C} \times \vec{B} + \vec{C} \times \vec{C} \right) \] ### Step 3: Simplify using properties of cross product We know that the cross product of any vector with itself is zero, i.e., \( \vec{B} \times \vec{B} = 0 \) and \( \vec{C} \times \vec{C} = 0 \). Thus, we can simplify: \[ = \vec{A} \cdot \left( \vec{B} \times \vec{A} + \vec{B} \times \vec{C} + \vec{C} \times \vec{A} + \vec{C} \times \vec{B} \right) \] ### Step 4: Evaluate the dot products Now we can evaluate the dot products: 1. \( \vec{A} \cdot (\vec{B} \times \vec{A}) = 0 \) (since the dot product of a vector with the cross product of itself and another vector is zero). 2. \( \vec{A} \cdot (\vec{C} \times \vec{C}) = 0 \) (same reasoning). 3. \( \vec{A} \cdot (\vec{B} \times \vec{C}) \) remains as is. 4. \( \vec{A} \cdot (\vec{C} \times \vec{B}) \) also remains as is. Thus, we have: \[ = 0 + 0 + \vec{A} \cdot (\vec{B} \times \vec{C}) + \vec{A} \cdot (\vec{C} \times \vec{B}) \] ### Step 5: Use the scalar triple product property Using the property of scalar triple product, we know that \( \vec{A} \cdot (\vec{B} \times \vec{C}) = \vec{B} \cdot (\vec{C} \times \vec{A}) \). Therefore, we can simplify: \[ = 0 + 0 = 0 \] ### Conclusion Thus, the final answer is: \[ \vec{A} \cdot (\vec{B} + \vec{C}) \times (\vec{A} + \vec{B} + \vec{C}) = 0 \] ### Final Answer The correct option is (A) 0. ---

To solve the problem, we need to evaluate the expression \( \vec{A} \cdot (\vec{B} + \vec{C}) \times (\vec{A} + \vec{B} + \vec{C}) \). ### Step 1: Expand the expression We start by expanding the expression using the distributive property of the dot product and the cross product. \[ \vec{A} \cdot (\vec{B} + \vec{C}) \times (\vec{A} + \vec{B} + \vec{C}) = \vec{A} \cdot \left( \vec{B} \times (\vec{A} + \vec{B} + \vec{C}) + \vec{C} \times (\vec{A} + \vec{B} + \vec{C}) \right) \] ...
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