Question
If $ \vec{a} + \vec{b} + \vec{c} = \vec{0} $, and $ |\vec{a}| = 3 $, $ |\vec{b}| = 5 $, $ |\vec{c}| = 7 $, then the angle between $ \vec{a} $ and $ \vec{b} $ is:
If $ \vec{a} + \vec{b} + \vec{c} = \vec{0} $, and $ |\vec{a}| = 3 $, $ |\vec{b}| = 5 $, $ |\vec{c}| = 7 $, then the angle between $ \vec{a} $ and $ \vec{b} $ is: