Establish the Identity $$\cos ( x - y ) - \cos ( x + y ) = 2 \sin x \sin y$$

question 119

Essay

Establish the identity.
- $$\cos ( x - y ) - \cos ( x + y ) = 2 \sin x \sin y$$

---

Definitions:

Liabilities

Financial obligations or debts owed by an individual, company, or entity to other parties.

United States Treasury Securities

Debt securities issued by the U.S. government to fund its budget deficits and manage the national debt.

Open Market

A venue where buyers and sellers engage in the trade of commodities, securities, and other financial instruments under defined regulations.

Reserve Ratio

The fraction of deposits that banks are required to keep on hand as reserves, determined by central banking authorities.