1. The problem statement, all variables and given/known data If a and b are vectors such that|a|=|b|=|a-b|, what is then the angle between a and b? What changes for |a|=|b|=|a+b| 2. Relevant equations 3. The attempt at a solution |a|=|b| ⇔ a=b ∴ a=b ⇔|a-b|=0 ...identity of discernibles angle between them is then 0. |a|=|b|=|a+b| ⇔ |a+b| = |2a| or |2b| = |2||a| = 2|a|. The magnitude of a or b changes but angle between a and b is 0 since a=b. Is this correct logic?