（1）y=sinxcosx+sinx+cosx
令t= sinx+cosx=√2sin(x+∏/4),∴t∈[-√2,√2]
则,t^2=(sinx+cosx)^2=1+2sinxcosx
则,sinxcosx=(t^2-1)/2
∴y=t+(t^2-1)/2=(1/2)t^2+t-(1/2)
令y=g(t)= (1/2)t^2+t-(1/2),t∈[-√2,√2]
对称轴是t=-1,开口向上
∴最大值y=g(√2)= (1/2)( √2)^2+√2-(1/2)
=√2+1/2
最小值y=g(-1)= (1/2)( -1)^2+(-1)-(1/2)
=-1
所以,值域是[-1,√2+1/2]
(2) y=cos(2x/5)+sin(2x/5)= √2sin[(2x/5)+∏/4]
∴最小正周期是T=2∏/(2/5)=5∏
∴相邻两条对称轴之间距离是d= T/2=5∏/2
(3) ∵4tan(a/2)=1-〔tan(a/2)〕^2
∴2tan(a/2)/{1- [tan (a/2)]^2}=1/2
∴tana=2tan(a/2)/{1- [tan (a/2)]^2}=1/2
又∵0