Question

Зная что tga+ctga=2,5, найдите tg²a+ctg²a.

Answer 1

$tg(a) +ctg(a) = 2.5\\\\(tg(a) +ctg(a))^{2} = 2.5^{2} \\\\tg(a)^{2} +ctg(a)^{2} +2tg(a)ctg(a) = 6.25\\\\tg(a)^{2} +ctg(a)^{2} +2 = 6.25\\\\tg(a)^{2} +ctg(a)^{2} = 4.25$   Форума : tg(x) * ctg(x) = 1

Ответ : 4.25