Find the product of the complex numbers. Express your answer in trigonometric form.
z1 = 5(cos(25) + isin(25))
z2 = 2(cos(80) + isin(80))

A. z1 = 3(cos(-55) + isin(-55))
B. z1 = 10(cos(105) + isin(105))
C. z1 = 7(cos(105) + isin(105))
D. z1 = 10(cos(305) + isin(305))

Question

Find the product of the complex numbers. Express your answer in trigonometric form.
z1 = 5(cos(25) + isin(25)) 
z2 = 2(cos(80) + isin(80))

 		A.	z1 = 3(cos(-55) + isin(-55))
 		B.	z1 = 10(cos(105) + isin(105))
 		C.	z1 = 7(cos(105) + isin(105))
 		D.	z1 = 10(cos(305) + isin(305))

tkhunny · Answer

#1 It makes no sense to have "z1" in all the answer, unless we're not supposed to notice that nothing matches the original definition.

#2  How does DeMoivre work?  If z1 were equal to z2, what would happen?

tkhunny · Answer

@eashy Please, never do that again.  Read the code of conduct and consider compliance.

anonymous · Answer

?

tkhunny · Answer

From the Code of Conduct

"Give Help, Not Answers
    I will encourage and guide those needing help, and not just give them an answer"

anonymous · Answer

ok. use the transformation e^ix=cos(x)+i sin(x) to convert multiplication into addition
(cos(25) + isin(25))*(cos(80) + isin(80))=e^25i*e^80i=e^105i=cos(105) + isin(105)