ex X + 1 1 . If f ( X ) = ( ex + 1 ) cosky ), what is the value of f' (0) ? a ) 9/ 2 6 ) 3 / 2 ( ) 5 / 2 1 ) 1 / 2 e ) 7 / 2 2 . At which X-value (s ) does the function f ( x ) = en (x ) have horizontal tangent lines ? 2 a ) x = e z only b ) x = e only CS x = ez only d ) x = 0 and x = e