Thus, for a given non zero complex number , its modulus and argument can be computed so that can be represented as . This representation is called the polar representation of , and the values of and are called polar coordinates of . Writing as is known as the trigonometric form of the complex number .
For the complex number , the modulus is , but the argument is undefined . If a complex number is written in the polar form or in the trigonometric form then it is understood that it is a non-zero complex number.
For each non-zero , there is only one value of say satisfying . This value will henceforth be denoted by and is called the principal value of . We can establish the relation between and :

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