Q)
If $ \overrightarrow a + \overrightarrow b + \overrightarrow c = 0\: and\: | \overrightarrow a | = 3, |\overrightarrow b | = 5\: and \: |\overrightarrow c | = 7 .$Show that the angle between \( \overrightarrow a \: and \overrightarrow b\) is \( 60^{\circ} \)
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