# Expand Using Sum/Difference Formulas cos(45)

Expand Using Sum/Difference Formulas cos(45)
The angle is an angle where the values of the six trigonometric functions are known. Because this is the case, add to keep the value the same.
Use the sum formula for cosine to simplify the expression. The formula states that .
The exact value of is .
The exact value of is .
The exact value of is .
The exact value of is .
Simplify each term.
Multiply by .
Multiply by .