- [math]2 i[/math].
- [math]\pi i[/math].
- a Real Number.
- See: Complex Number, Imaginary Unit, Square (Algebra), Real Part, Modular Arithmetic.
- (Wikipedia, 2014) ⇒ http://en.wikipedia.org/wiki/Imaginary_number Retrieved:2014-10-16.
- An imaginary number is a number that can be written as a real number multiplied by the imaginary unit ,[note 1] which is defined by its property .  The square of an imaginary number is . For example, is an imaginary number, and its square is . Except for 0 (which is both real and imaginary  ), imaginary numbers produce negative real numbers when squared. An imaginary number can be added to a real number to form a complex number of the form , where the real numbers and are called, respectively, the real part and the imaginary part of the complex number.[note 2] Imaginary numbers can therefore be thought of as complex numbers whose real part is zero. The name "imaginary number" was coined in the 17th century as a derogatory term, as such numbers were regarded by some as fictitious or useless. The term "imaginary number" now means simply a complex number with a real part equal to, that is, a number of the form .
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