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Use an Identity to find the exact value of the expression

Use An Identity To Find The Exact Value Of The Expression class=

Sagot :

Answer:

[tex]\cos(\frac{7\pi}{8})=-\sqrt{\frac{\sqrt{2}+1}{2\sqrt{2}}}[/tex]

Explanation:

First, we can note that:

[tex]\frac{7\pi}{8}=\pi-\frac{\pi}{8}[/tex]

Then:

[tex]\cos(\frac{7\pi}{8})=\cos(\pi-\frac{\pi}{8})[/tex]