确定tan(-17π/5)符号,

问题描述:

确定tan(-17π/5)符号,

tan(-17π/5)
=tan(4π-17π/5)
=tan(3π/5)

tan(-17π/5)
=tan[-4π+(3π/5)]
=tan(3π/5)
而角3π/5是第二象限角,则:tan(3π/5)