Объяснение:

[tex]\frac{2*sin18^0*cos18^0*cos36^0}{2*cos18^0} =\frac{sin36^0*cos36^0}{2*cos18^0} =\frac{2*sin36^0*cos36^0}{2*2*cos18^0} =\frac{sin72^0}{4*cos18^0}=\\ =\frac{sin(90^0-18^0)}{4*cos18^0} =\frac{cos18^0}{4*cos18^0} =\frac{1}{4}=0,25.[/tex]