OpenStudy (anonymous):

simplify (1-i(1/root3))^10 using demoivres theorem I got to this stage 1024/243 * (cos10pi/6+isin10pi/6) which almost gives me the right answer but it has a negative. and in the answer to the question both complex and real parts are positive

5 years ago
OpenStudy (anonymous):

what did you find for the angle?

5 years ago
OpenStudy (anonymous):

angle should be $$-\frac{\pi}{6}$$ or $$\frac{11\pi}{6}$$ so when you multiply by ten you get $$-\frac{5\pi}{3}$$ or $$\frac{\pi}{3}$$ which is why both parts are positive

5 years ago
OpenStudy (anonymous):

thanks! i've solved it. but why do u say or 11pi/6? why is there two angles?

5 years ago
OpenStudy (anonymous):

the angle is not unique when you write $$a+bi=r(\cos(\theta)+i\sin(\theta))$$ any coterminal angle will do

5 years ago
OpenStudy (anonymous):

ah i see, they both give the same value. Thanks again!

5 years ago
OpenStudy (anonymous):

so you can choose $$-\frac{\pi}{6}$$ or $$\frac{11\pi}{6}$$ or anything coterminal

5 years ago
OpenStudy (anonymous):

yw

5 years ago
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