Complex Numbers Multiplication

Complex Numbers Multiplication

 

The complex numbers obey the commutative, associative, and distributive laws. But although the property \sqrt{a} \sqrt{b} = \sqrt{ab} dose not hold for complex numbers in general, it does hold when a = -1 and b is a positive real number.

To multiply square roots of negative real numbers, we first express them in terms if i .

For example,

\sqrt{-2} . \sqrt{-5} = \sqrt{-1} . \sqrt{2} . \sqrt{-1} . \sqrt{5} = i\sqrt{2} . i\sqrt{5}

= i2\sqrt{10} = –\sqrt{10} is correct!

But  \sqrt{-2} . \sqrt{-5} = \sqrt{(-2)(-5)} = \sqrt{10} is wrong!

Keeping this and the fact that i2 = -1 in mind, we multiply in much the same way that we do with real numbers.

 

Leave a Reply

Your email address will not be published. Required fields are marked *