If a , b , c are the three unit vectors such that | a + b + c |=1 and b is perpendicular to c . If a makes angles , with b and c respectively, then + has the value

Step-by-step solution

aligned & | a + b + c |^2=| a |^2+| b |^2+| c |^2+2 a b +2 b c +2 c a & 1^2=1^2+1^2+1^2+2 & | a || b | +2| b || c | 90^ +2| c || a | & 1+3+2 +2 0+2 & + =-1 aligned