Ответ:
1.sin^2(a)
2.39
3.sin(a)
4.cos(a)
5. 1
Объяснение:
1. 1-cos^2(a)=sin^2(a)
2. 38+sin^2(a)+cos^2(a)=39
3. cos(a)*tg(a)=sin(a)
4. tg(a)*ctg(a)-1+sin(a)*ctg(a)=1-1+cos(a)=cos(a)
5. (1-cos(a))*(1+cos(a))=1-cos^2(a)=sin^2(a)
sin^2(a)/sin^4(a)=1/sin^2(a)
1/sin^2(a)- ctg^2(a)=(1-cos^2(a))/sin^2(a)=1