Question

已知sin(π+α)=4/5(α为第四象限角),求cos(π+α)+tan(-α)的值

Answer 1

sin(π+α)=4/5(α为第四象限角),
sinα=-4/5,cosα=3/5,tanα=-4/3,
∴原式=-cosα-tanα=-3/5+4/3=11/15.

Answer 2

因为sin(π+α)=4/5；
所以sina=-4/5.

cos(π+α)+tan(-a)
=-cosa-tana
=-3/5-(-4/3)
=-3/5+4/3
=11/15.