Two vectors X and Y have equal magnitude. The magnitude of ( X - Y ) is n times the magnitude of ( X + Y ). The angle between X and Y is:

Two vectors $\displaystyle \vec{X}$ and $\displaystyle \vec{Y}$ have equal magnitude. The magnitude of $\displaystyle (\vec{X}-\vec{Y})$ is $\displaystyle n$ times the magnitude of $\displaystyle (\vec{X}+\vec{Y})$. The angle between $\displaystyle \vec{X}$ and $\displaystyle \vec{Y}$ is: