Find the Exact Value Under the Given Conditions Find $\cos ( \alpha + \beta )$

question 48

Multiple Choice

Find the exact value under the given conditions.
- $\cos \alpha = - \frac { 4 } { 5 } , \frac { \pi } { 2 } < \alpha < \pi ; \quad \sin \beta = - \frac { \sqrt { 21 } } { 5 } , \pi < \beta < \frac { 3 \pi } { 2 } \quad$ Find $\cos ( \alpha + \beta )$ .

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

---

Definitions:

Continuous Section Break

A document formatting feature that allows different sections to seamlessly flow within the same page or column.

Go To Command

A function in software that allows users to jump directly to a specified location or element, such as a page number in a document.

Next Section

Refers to the subsequent part or segment in a document or presentation.

Navigation Pane

A user interface component that provides a structured and easy way to browse different sections or features within an application.