Pay attention to the word geometrically.
Squaring both sides we get a?a+b?b + c?c -2a?b- 2b?c -2c?a =0
Now a?a has 0 degree angle between so it is zero similarly b?b and c?c will also be zero now
-2a?b- 2b?c -2c?a =0
Taking 2 common
We get
a?b + b?c +c?a=0
Hope it helps.
Now a?a has 0 degree angle between so it is zero similarly b?b and c?c will also be zero now
-2a?b- 2b?c -2c?a =0
Taking 2 common
We get
a?b + b?c +c?a=0
Hope it helps.