[sin(π+α)*cos(π-α)*tan(π-α)]/[cos(π/2+α)*tan(3π/2-α)*tan(α-3π)]=[(-sinα)*(-cosα)*(-tgα)]/[(-sinα)*ctgα*(tgα)]=[-sinα*cosα*tgα]/[-sinα*ctgα*tgα]=cosα/ctgα=cosαtgα诱导公式：s...