(a^-6*b^4*8c^3*a^6)/(4c^2*b^5)=2c/b
A/(a-1)(a+1)+(a²+a-1)/[a²(a-1)+(a-1)]+(a²-a-1)/[a²(a+1)+(a+1)]-2a³/(a²-1)(a²+1)=
=a/(a-1)(a+1)+(a²+a-1)/(a-1)(a²+1)+(a²-a-1)/(a+1)(a²+1)-2a³/(a-1)9a+1)(a²+1)=
=(a³+a+a³+a²+a²+a-a-1+a³-a²-a²+a-a+1-2a³)/(a-1)(a+1)(a²+1)=
=(a³+a)/(a²-1)9a²+1)=a(a²+1)/(a²-1)9a²+1)=a/(a²-1)
Tga=f`(x0)
f`(x)=√3/4cos²(x/4)
f`(2π/3)=√3:4cos²(π/6)=√3:4*3/4=√3/3
tga=1/√3
a=π/6