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  • Perplex

    Complex Numbers (Lesson 4/5)

    Complex Phasors

    1 / 5

    Discussion

    Consider the functions f(x)=3sin(x), g(x)=5sin(x+2π​). Let h(x)=f(x)+g(x).


    Our goal is to write h(x) in the form h(x)=Asin(x+B). Let's walk through how to do this step by step.

    (a)

    First, show that Im(rcis(ΞΈ)) is a sine function.

    Solution:

    We use the definition

    cis(ΞΈ)=cosΞΈ+isinΞΈ

    so

    rcis(ΞΈ)=r(cosΞΈ+isinΞΈ)=rcosΞΈ+irsinΞΈ

    Taking the imaginary part gives

    Im(rcis(ΞΈ))=rsinΞΈ

    which is exactly a sine function of ΞΈ with amplitude r.