Доказать тождество: 1)   sin^4-cos^4+2cos^2=1       2) cos/1-sin=1+sin/cos

1) [latex] (sin^{2} - cos^{2} )( sin^{2} + cos^{2} )+2 cos^{2} =1[/latex] [latex] sin^{2} - cos^{2} +2 cos^{2} =1[/latex] [latex] sin^{2} + cos^{2} =1[/latex] 1=1 2)[latex] \frac{cos}{1-sin} = \frac{1+sin}{cos} [/latex] [latex] \frac{ cos^{2} }{cos(1-sin)} = \frac{1- sin^{2} }{cos(1-sin)} [/latex] [latex] \frac{ cos^{2} }{cos(1-sin)} = \frac{ cos^{2} }{cos(1-sin)} [/latex]