If a + b + c = 0 ,| a |=3,| b |=5,| c |=7 , then the angle between a and b is

Step-by-step solution

Given, a + b + c = 0 array ll & c =-( a + b ) & | c |²= c c =( a + b ) ( a + b ) array array l | c |²=| a |²+| b |²+2 a b | c |²=| a |²+| b |²+2| a || b | 49=9+25+2 3 5 15=30 = 1 2 = 3 array