Use a Product-To-Sum Formula to Convert the Expression to a Sum

question 17

Multiple Choice

Use a product-to-sum formula to convert the expression to a sum or difference. Simplify where possible. $\cos \frac { \pi } { 5 } \cos \frac { 4 \pi } { 5 }$

• A) \(\frac { 1 } { 2 } \left( \cos \frac { 3 \pi } { 5 } + 1 \right)\)
• B) \(\frac { 1 } { 2 } \left( \cos \frac { 3 \pi } { 5 } - 1 \right)\)
• C) \(1 + \sin ^ { 2 } \frac { \pi } { 5 }\)
• D) \(- \frac { 1 } { 2 } \sin \frac { 3 \pi } { 5 }\)
• E) \(1 - \sin ^ { 2 } \frac { \pi } { 5 }\)

---

Definitions:

Equity Method

An accounting technique used to record investments in other companies, recognizing the investor's share of the investee's net income.

Parent Company

A company that holds enough voting stock in another firm to control management and operations by influencing or electing its board of directors.

Consolidated Financial Statements

Financial reports that combine the accounts of a parent company and its subsidiaries into a single document.

Fair Value Method

An accounting approach used to measure assets and liabilities at estimates of their current value, rather than at historical cost or intrinsic value.