问题
解答题
已知函数f(x)=2acos2x+
|
答案
f(x)=2acos2x+
asin2x+a+b3
=a(1+cos2x)+
asin2x+a+b3
=acos2x+
sin2x+2a+b3
=2asin(2x+
)+2a+bπ 6
∵0≤x≤π 2
∴
≤2x+π 6
≤π 6
-7π 6
≤sin(2x+1 2
)≤1π 6
当a＞0时2a+2a+b=1 -a+2a+b=-5 a=2 b=-7
当a＜0时 -a+2a+b=1 2a+2a+b=-5 a=-2 b=3
∴a=2，b=-7或a=-2，b=3