Question #e6daa

1 Answer
Aug 27, 2016

The complex conjugate of Re^(itheta)Reiθ is Re^(-itheta)Reiθ

Explanation:

Standard notation for the complex number sqrt(-1)1 is ii, and so that will be used in the answer.

Given a complex number ww with polar form Re^(itheta)Reiθ, we wish to find the complex conjugate w^"*"w* of ww in polar form. To do so, we will use Euler's formula : e^(itheta) = cos(theta)+isin(theta)eiθ=cos(θ)+isin(θ), along with the facts that the sine function is odd and the cosine function is even.

Proceeding,

(Re^(itheta))^"*"color(white)(_)=(R(cos(theta)+isin(theta)))^"*"(Reiθ)*_=(R(cos(θ)+isin(θ)))*

=(Rcos(theta)+iRsin(theta))^"*"=(Rcos(θ)+iRsin(θ))*

=Rcos(theta)-iRsin(theta)=Rcos(θ)iRsin(θ)

=R(cos(theta)-isin(theta))=R(cos(θ)isin(θ))

=R(cos(-theta)+isin(-theta))=R(cos(θ)+isin(θ))

=Re^(i(-theta))=Rei(θ)

=Re^(-itheta)=Reiθ