Question

If A+B=C,|A|=|B|=|C|,then the angle between A,B

Answer 1

Let |A| = | B| = |C| = x

Vector addition :  A+B = C
so  |C|² =|A|² + |B|² + 2 |A| * |B| * cos Ф
x² = x² + x² + 2 x² cosФ
Cos Ф = - 1/2 ...   Ф = 120°