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

question 237

Multiple Choice

Find the exact value of the expression using the provided information.
-Find $\cos ( s + t )$ given that $\sin s = - \frac { 1 } { 2 }$ , with $s$ in quadrant IV, and $\sin t = \frac { 1 } { 4 }$ , with $t$ in quadrant II.

• A) \(- \frac { 4 \sqrt { 3 } + \sqrt { 15 } } { 11 }\)
• B) \(\frac { 1 + 3 \sqrt { 5 } } { 8 }\)
• C) \(\frac { 1 - 3 \sqrt { 5 } } { 8 }\)
• D) \(\frac { 4 \sqrt { 3 } - \sqrt { 15 } } { 11 }\)

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