  In this paper, we establish the following version at infinity of Whitney's
theorem [6, 7]: Geometric and algebraic tangent cones at infinity of complex
algebraic varieties coincide. The proof of this fact is based on a geometric
characterization of geometric tangent cones at infinity and using the global \L
ojasiewicz inequality with explicit exponents for complex algebraic varieties.
We also show that tangent cones at infinity of complex algebraic varieties can
be computed using Gr\"obner bases.
