Question

Use an Identity to find the exact value of the expression

Answer 1

`\cos((7\pi)/(8))=-\sqrt{(√(2)+1)/(2√(2))}`

Step-by-step explanation:

First, we can note that:

`(7\pi)/(8)=\pi-(\pi)/(8)`

Then:

`\cos((7\pi)/(8))=\cos(\pi-(\pi)/(8))`