Re: Question on complex no 2

Hey Tutu.

The expansion is correct.

For the last part consider the fact that e^(a*i*theta) = cos(a*theta) + i*sin(a*theta) = (e^(i*theta))^a = (cos(theta) + i*sin(theta)^a.

Re: Question on complex no 2

Thank you!

But how can cos^4(a) be substituted in e^(a*i*theta) ?

And I cannot sub it into cos(a*theta) + i*sin(a*theta) either because I will have the extra isin(a)..

I tried it out in another way, is it that

z^4 + 4z^2 +6 +(4/z^2) + (1/z^4) = 2cos(4a)?

Re: Question on complex no 2

Consider that cos is the real part and sin is the imaginary part.