докажите тождество. ctg^2x-cos^2x=ctg^2 * cos^2

Ответ. (ctg(x))^2-(cos(x)^2=(ctg(x))^2*(cos(x))^2; (ctg(x))^2-(cos(x)^2=((cos(x))^2)*(1/((sin(x))^2)-1)=((cos(x))/(sin(x)))^2)*(1-((sin(x))^2)=((ctg(x))^2)*(cos(x))^2);