tan(-14π/15)=-tan(π/15)=tan(-π/15)对吗?
问题描述:
tan(-14π/15)=-tan(π/15)=tan(-π/15)对吗?
答
tan(-14π/15)=-tan(π/15)=tan(-π/15)不对,应为:
tan(-14π/15)
=tan(-π+π/15)
=tan(π/15)