COMPLEX NUMBERS , DEMOIVRE'S THEOREM & EULER'S FORM

       COMPLEX    NUMBERS

Any  number of the form  a+bi is known as  complex  number where a & b are real numbers & i=  √-1 , a is called real part & b is called imaginary part.

           A complex number is generally denoted by z. If a is 0 then 

      z is purely imaginary & if b is 0 then z is purely real.

NOTE:

  1) i  = √-1  

  2) i² = -1

  3) i³ = i² i =-1.i =-i

  4) i⁴ =i³.i =-i.i =-i² =-(-1) =1

  5) i⁵ = i⁴ .i =1.i =i

  6) i⁶ =i⁵.i = i.i = i² = -1

 7) i⁷ =i⁶ .i =-1. i =-i

 8 ) i⁸ =i⁷.i =-i.i =- i² = -(-1)=1

 9) i⁹ =  i⁸.i = 1.i =i

10)i¹º =i⁹.i =i.i =i² = -1

  &  so on .

Read blog on Line & it's Equation

                ALJEBRA OF COMPLEX NUMBERS

  1)  ADDITION : When two complex numbers 

   are added their sum is also a complex number.

   eg.

  if z₁=a₁+b₁i  & z₂=a₂+b₂i then z₁+ z₂ is given by

       z₁+ z₂ = (a₁+b₁i ) + (a₂+b₂i ) 

                  = (a₁+a₂) + (b₁+b₂)i

2)   SUBTRACTION : When two complex 

   numbers are subtracted their  difference is 

    also a complex number .

   eg.

    if z₁=a₁+b₁i  & z₂=a₂+b₂i then z₁-z₂ is given by

       z₁- z₂ = (a₁+b₁i ) - (a₂+b₂i ) 

                 = (a₁-a₂) + (b₁-b₂)i

2) MULTIPLICATION : When two complex numbers 

    are multiplied their multilication is also a complex number .

   eg.

 if z₁=a₁+b₁i  & z₂=a₂+b₂i then z₁. z₂ is given by

       z₁. z₂ = (a₁+b₁i ) . (a₂+b₂i ) 

                 = (a₁a₂-b₁b₂) + ( a₁b₂+b₂a₁)i

                 EQUALITY OF COMPLEX NUMBERS 

Two complex numbers are said to be equal if

1)Their real parts are equal

2)Their imaginary parts are also equal.

 eg. If z₁=a+bi  & z₂=2+3i 

             z₁=z₂ if a+bi  =2+3i i.e a=2 & b=3

         CONJUGATE OF A COMPLEX NUMBER

Two complex numbers which are differ only in the sign of their imaginary parts are said to be conjugates of each other.

If z is complex number then it's conjugate is denoted by z .ie. z bar.

if 2+3i is given complex number the it's conjugate is given by 2-3i.

          

                 z                              conjugate  z

          2+3i                                             2-3i.

               2-3i                               2+3i

             -2+3i                              -2-3i

             -2-3i                                -2+3i

              -3i                                     +3i

             +3i                                      -3i

NOTE : 1)SUM &product of two complex conjugates are real.

               2)difference of two complex conjugates are imaginary.

Read the blog on Pascal Triangle & FIBONACCI NUMBERS

                       MODULUS & ARGUMENTS

If z=a+bi is a complex number then modulus of z is given by r=√a²+b² .

Argument or amplitude of z is given by  𝛩＝tan⊣(y/x) 

i.e tan inverse of y/x

           POLAR FORM OF A COMPLEX NUMBER

IF z=a+bi is a complex number then it's 

   polar form is given by z=r(cos𝛩+ i sin 𝛩)

EXPONENTIAL FORM OF A COMPLEX NUMBER

1)   eⁱӨ = e raise to iӨ =cos Ө+i sinӨ

2) e⁻ⁱө  =e raise to -iө  =cos Ө-i sinӨ

3) eⁱӨ +e⁻ⁱө =2cosө

4) eⁱӨ - e⁻ⁱө =2isinө

  DE MOIVRE'S THEOREM

For any rational number n the value or one of the value of 

(cos Ө+i sinӨ)ⁿ= (cos nӨ+i sin nӨ)

e.g. 1) if (cos Ө+i sinӨ)⁴ = (cos 4Ө+i sin4Ө)

       2) if (cos Ө-i sinӨ)⁴ = (cos 4Ө-i sin4Ө)

      3)  if (cos Ө+i sinӨ)⁻⁴ = (cos 4Ө-i sin4Ө)

      4)  if (cos Ө-i sinӨ)⁻⁴ = (cos 4Ө+i sin4Ө)

EULER'S FORM 

1) if z₁=a₁+b₁i  & z₂=a₂+b₂i then r=√a²+b² .

&     z₁

__________=  ( r₁/r₂) eⁱ(ө₁-ө₂)      

     z₂                

2) z₁ . z₂  = (r₁.r₂) eⁱ(ө₁+ө₂)  

i.e    (r₁.r₂). e raise to i.(ө₁+ө₂)  

 This is known as Euler's form