Kenneth S. answered 04/29/18
I unveil the mysteries and secrets of trigonometry & you'll love it.
= 20 cis 420o = 20 cis 60o
Can you complete this task now?
What did you do?
What did I do? I did what DeMoivre's Theorem suggests: For two complex numbers r cis θ and s cis ω their product is
rs cis (θ+ω). Then I removed one full rotation (360 degrees) from the angle sum.
I advise you to study the theorems carefully, with attention to worked examples in the textbook.