2sinα^2α+1=(2sin^2 α-1)+2=2-cos2α
cos2α=(cos^2 α-sin^2 α)/(sin^2α+cos^2α)= (1-tan^2 α)/(1+tan^2 α)
=(1-4)/(1+4)=-3/5
2sinα^2α+1=(2sin^2 α-1)+2=2-cos2α=2+3/5=13/5