NDA 2025
- Exam
- NDA
- Year
- 2025
- Subject
- Mathematics
- Chapter
- Vector Algebra
NDA 2025 · Mathematics · Vector Algebra
Consider the following statements in respect of a vector d = ( a ×...
Consider the following statements in respect of a vector :
I. is coplanar with and .
II. is perpendicular to .
Which of the statements given above is/are correct?
I. is coplanar with and .
II. is perpendicular to .
Which of the statements given above is/are correct?
Options
- AI only
- BII only
- CBoth I and II
- DNeither I nor II
Correct answer
C. Both I and II
Step-by-step solution
Given
Using the vector triple product expansion:
This shows that is expressed as a linear combination of and . Thus, lies in the plane containing and , making it coplanar with and . Statement I is correct.
By the definition of the cross product, the vector resulting from the cross product of two vectors is perpendicular to both of them. Since is the cross product of and , it must be perpendicular to both and .
Therefore, , which means is perpendicular to . Statement II is correct.
Both statements I and II are correct.
Answer: Both I and II
Using the vector triple product expansion:
This shows that is expressed as a linear combination of and . Thus, lies in the plane containing and , making it coplanar with and . Statement I is correct.
By the definition of the cross product, the vector resulting from the cross product of two vectors is perpendicular to both of them. Since is the cross product of and , it must be perpendicular to both and .
Therefore, , which means is perpendicular to . Statement II is correct.
Both statements I and II are correct.
Answer: Both I and II