# Expand Using Sum divide Difference Formulas cos(three hundred forty minus five)

Expand Using Sum/Difference Formulas cos(345)
First, split the angle into two angles where the values of the six trigonometric functions are known. In such a case, can be split into .
Use the sum formula for cosine to Clarify the expression. The formula states that .
The exact value of is .
Clarify .
Use the reference angle by calculating the angle with equivalent triginometric values in the Initially quadrant.
The exact value of is .
The exact value of is .
Simplify .
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Should be rewritten the expression as a negative one since sine is negative in the 2nd quadrant.
The exact value of is .
Clarify each term.
First, multiply .
Multiply and .
First, multiply by .
Multiply .
Multiply by .
Multiply by .
Multiply and .