Answer:
-10/3 is the answer
Step-by-step explanation:
Given are two complex numbers as
[tex]z1=\frac{2}{5} (cos63 + isin63)\\z2=\frac{10}{3} (cos 117 + isin117})[/tex]
Recall Demoivre theorem as
(cosA+isinA)(cos A+isin B) = cos(A+B)+isin(A+B)
Hence here we have sum of angles as
A+B = 63+117 =180
[tex]z1z2=\frac{2}{5} \frac{10}{3} (cos180+isin180)[/tex]
=[tex]\frac{-10}{3}[/tex]
Since sin180=0 and cos 180=-1
