Use the Dot Product to Find the Magnitude of U $\mathbf { u } = \langle - 7,12 \rangle$

Multiple Choice

Use the dot product to find the magnitude of u. ​​ $\mathbf { u } = \langle - 7,12 \rangle$ ​

A) $3 \sqrt { 21 }$
B) $\sqrt { 195 }$
C) $\sqrt { 197 }$
D) $\sqrt { 193 }$
E) $\sqrt { 191 }$