Find the Exact Value of the Expression Using the Provided $\cos ( \mathrm { s } + \mathrm { t } )$

question 372

Multiple Choice

Find the exact value of the expression using the provided information.
-Find $\cos ( \mathrm { s } + \mathrm { t } )$ given that $\sin \mathrm { s } = - \frac { \sqrt { 3 } } { 3 }$ , with $\mathrm { s }$ in quadrant IV, and $\sin \mathrm { t } = - \frac { \sqrt { 5 } } { 6 }$ , with $\mathrm { t }$ in quadrant
IV.

• A) \(\frac { \sqrt { 186 } + \sqrt { 15 } } { 18 }\)
• B) \(\frac { \sqrt { 186 } - \sqrt { 15 } } { 18 }\)
• C) \(\frac { \sqrt { 55 } + \sqrt { 15 } } { 18 }\)
• D) \(\frac { \sqrt { 55 } - \sqrt { 15 } } { 18 }\)

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