Question

已知函数f(x)=Asin(wx+φ)(A>0,w>0,|φ|

Answer 1

答：

1）

最低点Q（-π/6,-2),则A=2

f(-π/6)=2sin(-wπ/6+b)=-2,sin(-wπ/6+b)=-1,b-wπ/6=-π/2

f(π/12)=2sin(wπ/12+b)=0,wπ/12+b=0

由上两式解得：w=2,b=-π/6

f(x)=2sin(2x-π/6)

2)

f(a+π/12)=2sin[2(a+π/12)-π/6]=3/8

sin2a=3/16,1+sin2a=19/16

(sina+cosa)^2=19/16

a是第三象限角,sina