1) Quadratic irrational number 2) The complex number i 
The imaginary unit or unit imaginary number, denoted as {mvar|i}, is a mathematical concept which extends the real number system {math|ℝ} to the complex number system {math|ℂ}, which in turn provides at least one root for every polynomial {math|P(x)} (see algebraic closure and fundamental theorem of algebra). The imaginary unit`s core propert....
the complex number i.