(2*sin⁴(x/2)-1)*(1/cos⁴(x/2)=2
2*sin⁴(x/2)-1=2*cos⁴(x/2)
2*cos⁴(x/2)-2*sin⁴(x/2)=-1
2*(cos⁴(x/2)-sin⁴(x/2)=-1
(cos²(x/2)-sin²(x/2))*(cos²(x/2)+sin²(x/2))=-1/2
cosx*1=-1/2
cosx=-1/2
x₁=2π/3+2πn x₂=4π/3+2πn.
<span>-20sin1°/ sin359°=-</span>20sin(360-359)/ sin359°=-20sin<span><span>359°</span>/ sin359°</span>=-20
1) cos²x/2-sin²x/2=0, это косинус двойного угла, cosx=0, x=π/2+πn,n∈Z