Verify a trig identity

(sin x - cos x)(sin x + cos x) = 1- 2cos^2

So I foiled the left side and got this

sin^2 - cos^2 = 1 - 2cos^2

Now I'm stuck. Help please?

sin^2+cos^2=1
sin^2=1-cos^2

(sin-cos)(sin+cos)
sin^2-cos^2
1-cos^2-cos^2
1-2cos^2