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De Moivre's formula using prove that,
written 2.1 years ago by | • modified 2.1 years ago |
If $a=\cos \theta+i \sin \theta, b=\cos \phi+i \sin \phi$ prove that
(i) $\cos (\theta+\phi)=\frac{1}{2}\left[a b+\frac{1}{a b}\right]$
(ii) $\sin (\theta-\phi)=\frac{1}{2 i}\left[\frac{a}{b}-\frac{b}{a}\right]$
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