Есть формулы: SinαCosβ - CosαSinβ = Sin(α-β)
2SinαCosα = Sin2α
a) = Sin(57° -12°) = Sin45° = √2/2
б) = Sin2*75° = Sin150° = Sin(180° - 30°) = Sin30° = 1/2
Sina^2+cosa^2=1
sin^2+(4|5)^=1
sin^2+16|25=1
sin^2=1-16|25
sin^2=25|25-16|25
sin^2=9|25
sin=3/5
ctg=cosa|sina=4|5:3|5=4/3
tg=sin|cos=3|5:4|5=3|4
В) y:4/5=3 1/8*1 1/4
y:4/5=25/8:5/4=25/8*4/5=5/2
y=5/2
y=5/2*4/5=2/1
y=2