Question

Ctg2a-cos2a=ctg2a*cos2a докажите​

Answer 1

Ответ:

Объяснение: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)