Tga + ctga =Aнайдите tg^2a + ctg^2a ?????

Question

Tga + ctga =A
найдите tg^2a + ctg^2a ?????

Answer 1

Tg a * ctg a = 1; ⇒
 (tg a + ctg a)^2 = tg^2 a + 2 tga * ctg a + ct^2 a = tg^2 a + ctg^2 a + 2*1;
A = tg^2 a + ctg^2 a + 2; 
tg^2 a + ctg^2 a = A - 2