1) 1,64:1,6=1⁶⁴/₁₀₀:1⁶/₁₀=1¹⁶/₂₅:1³/₅=(41/25):(8/5)=41*5/(25*8)=41/40.
2) 0,625-(41/40)=(625/1000)-(41/40)=(25/40)-(41/40)=-16/40=-2/5.
3) 4¹/₆*(-2/5)=(25/6)*(-2/5)=-25*2/(6*5)=-5/3.
sin4xcos2x-sin2xcos4x=0
sin(4x-2x)=0
sin2x=0
x=П+2ПК, К принадлежит Z