Solution (source code)

= Solution

Three <vectors> form a <basis> of $\mathbb R^3$ exactly when they are <linearly independent>. The <determinant> with those <vectors> as columns is their <scalar triple product>, so the condition is
$$
\boxed{A\cdot(B\times C)\ne0.}
$$
Geometrically their <parallelepiped> must have nonzero <volume>.