Выражение 1. cos^2x-(ctg^2+1)*sin^2x 2.sin^2x-1/1+sinx +tgx*ctgx 3.sinx/1+cosx/ +sinx/1-cosx 4. ctg^2x*(cos^2x-1)+1 5. cosx/1+sinx +cosx/1-sinx 6.tgx+1/1+ctgx

1. =cos^2x-cos^2x+sin^2x=sin^2x
2. =(sinx-1)*(sinx+1)/(1+sinx)+1= sinx-1+1=sinx
3. =(sinx*(1-cosx)+sinx*(1+cosx))/(1+cosx)*(1-cosx)=(sinx-sinx*cosx+sinx+sinx*cosx)/(1-cos^2x)=2*sinx/sin^2x=2/sinx
4. =ctg^2x*(-sin^2x)+1=-cos^2x+1=sin^2x
5. =(cosx*(1-sinx)+cosx*(1+sinx))/(1+sinx)(1-sinx)=(cosx-cosx*sinx+cosx+cosx*sinx)/(1-sin^2x)=
2cosx/cos^2x=2/cosx
6. =((sinx+cosx)/cosx)/(cosx+sinx)/sinx=sinx/cosx=tgx