Use the Given Information to Find the Exact Value of the Expression

question 126

Multiple Choice

Use the given information to find the exact value of the expression.
- $\cos \alpha = - \frac { 4 } { 5 } , \alpha$ lies in quadrant III, and $\sin \beta = \frac { \sqrt { 21 } } { 5 } , \beta$ lies in quadrant II $\quad$ Find $\cos ( \alpha + \beta )$

• A) \(\frac { 8 + 3 \sqrt { 21 } } { 25 }\)
• B) \(\frac { - 8 - 3 \sqrt { 21 } } { 25 }\)
• C) \(\frac { 6 - 4 \sqrt { 21 } } { 25 }\)
• D) \(\frac { - 6 + 4 \sqrt { 21 } } { 25 }\)

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Definitions:

Net Operating Income

Income generated from normal business operations, excluding taxes and interest.

Relevant Costs

Costs that will be affected by a decision in the future and are pertinent to a specific business decision.

Alternative B

A second or other option in a set of choices, commonly referred to in decision-making scenarios or proposals.

Alternative A

A term that refers to one of several options or choices in a decision-making process, typically labeled as "Alternative A" for distinction.