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])

问题描述:

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])

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