√
4.4 28 y = cos x + 3 sin x = 2( 12 cos x +
(or correctly show y 0 and y 00 )
√
3
2
sin x) = 2 sin(x + π6 ) (5pt)
2pt for maximum and minimum value
3pt for zero pt and extreme value pts
4.5 72 use the sign of f 0 (x) and f 00 (x) to divide real line into different intervals
3pt for monotinicity on 3 intervals
2pt for concavity on 2 intervals
1
2
3