What is an imaginary number?

Answer 1

The square root of a negative real number is an imaginary number.

We know square root is defined only for positive numbers.

For example,

1) Find the square root of (-1)

It is imaginary. We say that square root of (-1) is i.

In fact they are not real numbers.

2) Find the square root of (-4)

-4 can be written as (-1)(4)

Square root of 4 is 2 and square root of (-1) is i

So, the square root of -4 is 2i.

Similarly, we can find the square root of other negative numbers also.

Source: www.icoachmath.com
An imaginary number is defined to handle square roots of negative numbers. The imaginary unit i is defined as the 'positive' square root of -1.