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

question 245

Multiple Choice

Find the exact value under the given conditions.
- $\sin \alpha = - \frac { 24 } { 25 } , \pi < \alpha < \frac { 3 \pi } { 2 } ; \quad \tan \beta = - \frac { 2 \sqrt { 21 } } { 21 } , \frac { \pi } { 2 } < \beta < \pi \quad$ Find $\cos ( \alpha + \beta )$

• A) \(\frac { 48 - 7 \sqrt { 21 } } { 125 }\)
• B) \(\frac { 48 + 7 \sqrt { 21 } } { 125 }\)
• C) \(\frac { 14 - 24 \sqrt { 21 } } { 125 }\)
• D) \(\frac { - 14 - 24 \sqrt { 21 } } { 125 }\)

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