Given 2 vectors in $\mathbb{R}^3$, $A$ and $B$, and the condition $\|A-B\|=\|A\|$. How can I find the angles that the vectors A and B could form?
I've started with: $\cos\theta=\frac{AB}{\|A\|\cdot\|B\|}$, and trying to derive some trick to relate the angle between $A-B$ and $B$ but it leads me nowhere.