How do I find the answer to e^i(pi/18) *without* using a calculator.
Thanks
Use Euler's Formula thus,Originally Posted by chancey
$\displaystyle e^{i(\pi/18)}=\cos (\pi/18)+i\sin(\pi/18)$
All you need to do is find what (co)sine of $\displaystyle \pi/18$ is, you can do this by using the third angle identity,
$\displaystyle
\cos 3\theta=4\cos^3 \theta-3\cos \theta
$
Which reduces to solving a cubic equation.