But and

2)use an identity to find an exact value for sin 105degrees.

answer:root6+root2/4

Use the double angle formula:

put , since you already know .

DO you mean sin of 22.5 degrees or cosine of 22.5 degrees? Whoat does the phrase "exact value of 22.5 degrees mean"?3)use an identity to find an exact value for 22.5degrees.

answer:root2-1