==>sin(π/4-a)=0==>a1=π/4,a2=-3π/4(舍)
(2)解析：∵函數f(x)=sin(wx+π/4),對於任意實數k,函數f(x)在區間(k,k+π/3]內恰有壹個最大值和壹個最小值
又函數f(x)初相為π/4,∴當x由0開始變化時,處於上升沿,即f(x)增大,距離Y軸最近的是最大值；兩個相鄰最值之間相差T/2
由0開始,第壹周期的最小值點小於π/3
f(x)=sin(wx+π/4)=-1==>wx+π/4=3π/2==>x=5π/(4w)
令5π/(4w)w>=15/4
由0開始,第二周期的最大值點大於π/3
f(x)= sin(wx+π/4)=1==>wx+π/4=2kπ+π/2==>x=2kπ/w+π/(4w)
令2π/w+π/(4w)> π/3==>w