Find ( int_{ /4}^{ /2}7 ,cos x ,dx ).

• A. 7(1- ( frac{1}{ sqrt{2}} ))
• B. -7(1- ( frac{1}{ sqrt{2}} ))
• C. 7(1+ ( frac{1}{ sqrt{2}} ))
• D. 7( ( sqrt{2}- frac{1}{ sqrt{2}} ))