I have come so far: =cis(4∏/5) + cis(6∏/5) + cis(-8∏/5) + cis(8∏/5) =2cos(4∏/5) + 2cos(8∏/5) =? How do I solve this without using a calculator (answer should be -1)?
Follow Math Help Forum on Facebook and Google+
Check out the trig identities.
View Tag Cloud