Sec^2(x)*(1-cos^2(x))=tan^2(x)

I need step by step help

1) sec^2x * sin^2x = tan^2x (proof sin^2x+cos^2x=1)
2) 1/(cos^2x) * sin^2x = tan^2x (sec^2x = 1/cos^2x)
3) (sin^2x)/(cos^2x)=tan^2x (combine sin^2x and 1/cos^2x)
4) tan^2x=tan^2x (sin^2x/cos^2x= tan^2x)