tg^2 a+1=1/cos^2 a
cos^2 a=1/(tg^2 a+1)=1/(121+1)=1/122
36cos^2=36/122=18/61
1)Применим формулу:
1/cos^2(a)= 1+ tg^2(a)
1/cos^2(a)= 1+ (-11)^2
1/cos^2(a)= 1+ 121
1/cos^2(a)= 122
cos^2(a)= 1/ 122
2)36*1/122 = 18/61
ответ: 18/61.
