Упростите 1) 1/cos^2 (a) – tg^2 (a) -sin^2 (a) 2) cos^2 (a)+ctg^2 (a) -1/sin^2 (a) 3) 1/cos^2 (a) – tg^2 (a) (cos^2 (a)+1) 4) (1+sin^2…

1) 1/cos^2 (a) – tg^2 (a) -sin^2 (a)=1/cos^2 (a) – sin^2 (a) /cos^2 (a) -sin^2 (a)=[1 – sin^2 (a) ]/cos^2 (a) -sin^2 (a)=cos^2 (a) /cos^2 (a) -sin^2 (a)=1-sin^2 (a)=cos^2 (a) 2) cos^2 (a)+ctg^2 (a) -1/sin^2 (a)=cos^2 (a)+[cos^2 (a) -1]/sin^2 (a)=cos^2 (a) -sin^2 (a) ]/sin^2 (a)=cos^2 (a) -1=-sin^2 (a) 3) 1/cos^2 (a) – tg^2 (a) (cos^2 (a)+1)=1/cos^2 (a) – sin^2 (a) -sin^2 (a) / (cos^2 (a)=(1 – sin^2 (a) /cos^2 (a) -sin^2 (a)=1-sin^2 (a)=cos^2 (a)