Use the Dot Product to Find the Magnitude of U $\mathbf { u } = \langle 2 , - 9 \rangle$

Multiple Choice

Use the dot product to find the magnitude of u.​ $\mathbf { u } = \langle 2 , - 9 \rangle$ ​

A) $\sqrt { 89 }$
B) $\sqrt { 83 }$
C) $\sqrt { 85 }$
D) $9$
E) $\sqrt { 87 }$