Simplify the following
A) (cosx - isinx)^5
B) (sinx - icosx)^4
for A i get
cos5x - isin5x
I think this is right...?
not sure if B is done the same or not. any help?
Hello,
Here is what you can do
De Moivre's formula says : $\displaystyle (\cos(x)+i\sin(x))^n=\cos(nx)+i \sin(nx)$
Remember that the sine function is odd and the cosine function is even.
So $\displaystyle (\cos(x)-i\sin(x))^n=(\cos(-x)+i \sin(-x))^n=$ $\displaystyle \cos(-nx)+i \sin(-nx)=\cos(nx)-i \sin(nx)$