Chọn trục quay tại O, ta có: \(� � . \overset{\rightarrow}{�} + � � . \overset{\rightarrow}{�} = \overset{\rightarrow}{0}\)

\(\Rightarrow \frac{1}{2} � � . � � - � � . � � � � 3 0^{0} = 0\)

\(\Leftrightarrow � = \frac{\frac{1}{2} � �}{� � � 3 0^{0}} = 14 \left(\right. � \left.\right)\)

Chọn trục quay tại O, ta có: \(� � . \overset{\rightarrow}{�} + � � . \overset{\rightarrow}{�} = \overset{\rightarrow}{0}\)

\(\Rightarrow \frac{1}{2} � � . � � - � � . � � � � 3 0^{0} = 0\)

\(\Leftrightarrow � = \frac{\frac{1}{2} � �}{� � � 3 0^{0}} = 14 \left(\right. � \left.\right)\)

Chọn trục quay tại O, ta có: \(� � . \overset{\rightarrow}{�} + � � . \overset{\rightarrow}{�} = \overset{\rightarrow}{0}\)

\(\Rightarrow \frac{1}{2} � � . � � - � � . � � � � 3 0^{0} = 0\)

\(\Leftrightarrow � = \frac{\frac{1}{2} � �}{� � � 3 0^{0}} = 14 \left(\right. � \left.\right)\)