The primary objects of study in differential geometry are ''smooth'' and ''Riemannian'' [[manifold|manifolds]]. A typical example of such an object is a smooth surface in R^3, for example, the unit sphere. Typical questions that a differential geometer might ask about a manifold include: | The primary objects of study in differential geometry are ''smooth'' and ''Riemannian'' [[manifold|manifolds]]. A typical example of such an object is a smooth surface in R^3, for example, the unit sphere. Typical questions that a differential geometer might ask about a manifold include: |