α是第三象限角：f(α)=[sin(π-α)cos(2π-α)tan(-α+（（3π）/2）)]/[cot(-α-π)sin(-π-α])

题目

α是第三象限角：f(α)=[sin(π-α)cos(2π-α)tan(-α+（（3π）/2）)]/[cot(-α-π)sin(-π-α])

答案

f(α)=sinacosacota/[cot(a+π)sin(a+π)]
=sinacosacota/(-cotasina)
=-cosa