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Fantom [35]
3 years ago
10

[2(cos15° + isin15°)]^4

Mathematics
1 answer:
Sergeu [11.5K]3 years ago
8 0

Answer:

8+8\sqrt{3} \ i

Step-by-step explanation:

[2(\cos15+i15)^{4}]\\=2^{4}(\cos15+i\sin15)^{4}\\=16(\cos15+i\sin15)^{4}..........(1)

<u>De Moivre's Formula :</u>

(\cos x+i\sin x)^{n}=\cos n x+i\sin nx\\\\\\(\cos 15+i \sin15)^{4}=\cos(4\times 15)+i\sin (4\times 15)\\=\cos60+i\sin60\\=\frac{1}{2} +\frac{\sqrt{3}}{2} \\=\frac{1+\sqrt{3i} }{2}

Now from eqn(1)

[2(\cos15+i\sin15)]^{4}=16\times \frac{1+\sqrt{3}i}{2} =8+8\sqrt{3}i

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3 years ago
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let

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y -------> speed of the current in km/hour



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