Use an Identity to find the exact value of the expression
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]