Use the dot product to find the magnitude of u if $\mathbf { u } = - 5 \mathbf { i } - 2 \mathbf { j }$
A) $\| \mathbf { u } \| =$ 10
B) $\| \mathbf { u } \| =$ $2 \sqrt { 29 }$
C) $\| \mathbf { u } \| = 7$
D) $\| \mathbf { u } \| = 15$
E) $\| \mathbf { u } \| =$ $\sqrt { 29 }$

Question

Quizplus · Accepted Answer

The magnitude of a vector $\mathbf{u} = a\mathbf{i} + b\mathbf{j}$ is given by $\|\mathbf{u}\| = \sqrt{a^2 + b^2}$. For $\mathbf{u} = -5\mathbf{i} - 2\mathbf{j}$, the magnitude is $\sqrt{(-5)^2 + (-2)^2} = \sqrt{25 + 4} = \sqrt{29}$.

Use the Dot Product to Find the Magnitude of U u=−5i−2j\mathbf { u } = - 5 \mathbf { i } - 2 \mathbf { j }u=−5i−2j

Use the Dot Product to Find the Magnitude of U $\mathbf { u } = - 5 \mathbf { i } - 2 \mathbf { j }$