Orthogonality between two characteristic subspaces that correspondence by non zero characteristic value of two real symmetric trausformations is discorused in this paper,than the Craig Theorem has become a corollaire too.

• 讨论了欧氏空间中的两个实对称变换的非零特征根的所对应特征子空间互相正交的充要条件 ,并用比较简捷的方法证明了定理 1 ,将它应用到概率论中证明了Craig定理。