由tan(α+ π 4 )= tanα+tan π 4 1?tanαtan π 4 = tanα+1 1?tanα =2,解得:tanα= 1 3 ,则sin2a+sinacosa= sin2α+sinαcosα sin2α+cos2α = tan2α+tanα tan2α+1 = ( 1 3 )2+ 1 3 ( 1 3 )2+1 = 2 5 .故答案为: 2 5