Exercise · ZW-VECTOR-NORM-007 · ★★☆ Intermediate
Find \(k>0\) such that \(\|(k,2k,2k)\|=12\).
Choose one option.
Show answer
- B. \(k=4\)
Explanation
\(\sqrt{k^2+4k^2+4k^2}=3k=12\), so \(k=4\).
Review the concept: Vector norm
The norm of a vector in \(\mathbb{R}^n\) is a nonnegative number measuring its length: the square root of the vector's dot product with itself.
\[\|x\|=\sqrt{x\cdot x}=\sqrt{x_1^2+\dots+x_n^2}\]
More practice problems: vector norm
- ZW-VECTOR-NORM-001 Compute \|(3,4)\|.
- ZW-VECTOR-NORM-002 Compute \|(1,2,2)\|.
- ZW-VECTOR-NORM-003 Compute \|(2,-3,6)\|.
- ZW-VECTOR-NORM-004 If \|v\|=4, what is \|3v\|?
- ZW-VECTOR-NORM-005 How do \|v\| and \|-v\| compare?
- ZW-VECTOR-NORM-006 Which unit vector points in the direction of (3,-4)?
- ZW-VECTOR-NORM-008 If \|u\|=3 and \|v\|=4, which of these values is impossible for \|u+v\|?
- ZW-VECTOR-NORM-009 If \|u\|=2, \|v\|=3 and u· v=-1, what is \|u+v\|?