# Expand Using Sum divide Difference Formulas cos((nineteen pi) divide twelve)

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 .

Use the reference angle by calculating the angle with equivalent triginometric values in the Initially quadrant. Make the expression negative because cosine is negative in the third quadrant.

The exact value of is .

The exact value of is .

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because sine is negative in the third quadrant.

The exact value of is .

First, multiply .

Multiply and .

First, multiply by .

Multiply .

Multiply by .

Multiply by .

Multiply and .

Add using the product rule for radicals.

Multiply by .

Multiply by .

Add numerators over the common denominator.

Factor out of .

Factor out of .

Factor out of .

Simplify the expression.

Should be rewritten as .

Put the negative in front of the fraction.

The result can be displayed in a variety of ways.

Exact Form:

Decimal Form:

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