1.
ctg 37π/6 =ctg(6π+π/6)=ctgπ/6=√3
cos(-1395)=cos 1395 град. =сos (3*360+315) =cos315 =cos(360-45)=cos45=√2/2
2.
sinα*cosα*tgα*ctgα=sinα*cosα =0.5sin2α
a) α=208 градусов 0,5sin2*208=0.5sin416=0.5sin (360+56)=0.5sin56
знак + так как 0<56 <90<br>b)α=3.1 радиан sin 3.1*2=sin6.2; 2π≈2*3.14=6.28; 1.5π≈1.5*3.14=4.71
3/2*π<2α<2π знак минус.<br>3.
оценить 2cos^2(x)-3; -1 ≤cosx≤1; 0 ≤cos^2(x)≤1; 0 ≤2cos^2(x)≤2
-3 ≤2cos^2(x)-3≤-1
4.
cos10x=√2/2
10x=+-arccos√2/2+2πk k∈Z
10x=+- π/4+2πk
x=+-π/40+0.2πk k∈Z