Домножим и разделим на cos(π/18)
(sinπ/18*cosπ/18*cosπ/9*cos2π/9)/cosπ/18=
=(sinπ/9*cosπ/9*cos2π/9)/(2cosπ/18)=
=(sin2π/9*cos2π/9)/(4cosπ/18)=
=(sin4π/9)/(8cosπ/18)=
=sin(π/2-π/18)/(8cosπ/18)=
=(cosπ/18)/(8cos(π/18)=
=1/8
Log1/7корень из 7 = x
(1/7)^x = корень из 7
7^-x= корень из 7
(корень из 7)^-2x = корень из 7
-2х = 1
х = -0,5
<em>(х − 7)(х + 7) = (х − 2)2 + 3</em>
в=-3а
(5а+3в)/(а-9а)=8а/(-8а)=-1