Тригонометрия, 10 кдасс

Это что

145
a
(1-cos(x)) * (1+cos(x) = sin^2(x)
sin^2(x) * ctg^2(x) = cos^2(x)

b
tg(x)*ctg(x) = 1
sin(x)*ctg(x) = cos(x)
1-cos^2(x) = sin^2(x)

c.
1+tg^2(x) = 1/cos^2(x)
1+ctg^2(x) = 1/sin^2(x)
cos^2(x) + sin^2(x) = 1




ctg(x) = 2
1+ctg^2(x) = 1/sin^2(x) = 5 -> sin(x) = -1/sqrt(5)
cos(x) = sqrt(1-1/5) = - 2/sqrt(5)
tg(x)*ctg(x) = 1 -> tg(x) = 1/2