sin^2α+2sinαcosα-3cos^2α
=(sin^2α+2sinαcosα-3cos^2a)/(sin^2α+cos^2α)
=(tan^2α+2tanα-3)/(tan^2α+1)
=(1/4-1-3)/(1/4+1)
=-15/5
=-3
sin^2α+2sinαcosα-3cos^2α
=(sin^2α+2sinαcosα-3cos^2a)/(sin^2α+cos^2α)
=(tan^2α+2tanα-3)/(tan^2α+1)
=(1/4-1-3)/(1/4+1)
=-15/5
=-3