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grandymaker [24]
3 years ago
15

Use a half-angle identity to find the exact solution of cos 3 pi / 8

Mathematics
2 answers:
Ratling [72]3 years ago
8 0

Answer:

-\sqrt{\frac{2-\sqrt{2}}{4}

Step-by-step explanation:

The cosine half-angle formula is

cos\frac{\pi }{2}=±\sqrt{\frac{1+cosx}{2} }

we can write

cos \frac{3\pi }{8}

as

cos\frac{\frac{3\pi }{4} }{2}

=-\sqrt{\frac{1+cos\frac{3\pi}{4} }{2}

=-\sqrt{\frac{1-\frac{\sqrt{2}}{2}}{2}

=-\sqrt{\frac{2-\sqrt{2}}{4}

(cosine is negative is in second quadrant)

AVprozaik [17]3 years ago
7 0

Answer:

A on edge

Step-by-step explanation:

pp smol

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