The function has a limit at if and only if one of its coordinate functions has a limit at .

In a vector sequence is convergent if and only if one of its coordinate coordinate sequence is convergent.

If the vectors  all have unit norms in an vector system, then it is an orthonormal system.

The distance is

If is an eigenvector of the linear transformation , then there exists a nonzero scalar , such that .

Let be an event and denotes the relative frequency of during independent experiment. Then for any one has

The cumulative density function of the exponential distribution is

• , if
• , if

Poisson distribution with parameter is the discrete probability distribution with possible values and probabilities

If is a random variable with values , … and probabilities , …, , then its expected value is

Let be a random variable with values ,, …and probabilities , …, Then the expected value is