1) sin α, cos α, tg α, ctg α для α = 421:

sin 421 = sin (2π + 61) = sin 61 > 0
cos 421 = cos (2π + 61) = cos 61 > 0
tg 421 = tg (2π + 61) = tg 61 > 0
ctg 421 = 1/tg 421 > 0

Значит, sin α, cos α, tg α, ctg α положительны для α = 421.

2) sin α, cos α, tg α, ctg α для α = 102:

sin 102 > 0, cos 102 < 0, tg 102 < 0, ctg 102 < 0

3) sin α, cos α, tg α, ctg α для α = 46π/9:

sin (46π/9) = sin (44π/9 + 2π/9) = sin (2π/9) > 0
cos (46π/9) = cos (44π/9 + 2π/9) = cos (2π/9) > 0
tg (46π/9) = tg (44π/9 + 2π/9) = tg (2π/9) > 0
ctg (46π/9) = 1/tg (46π/9) > 0

4) sin α, cos α, tg α, ctg α для α = 39π/10:

sin (39π/10) = sin (38π/10 + π/10) = sin (π/10) > 0
cos (39π/10) = cos (38π/10 + π/10) = cos (π/10) > 0
tg (39π/10) = tg (38π/10 + π/10) = tg (π/10) > 0
ctg (39π/10) = 1/tg (39π/10) > 0

Итак, sin α, cos α, tg α, ctg α положительны для α = 421, 46π/9 и 39π/10, но для α = 102 только sin α положительный.