已知tan(α+π/4）=-1/2,π/2
问题描述：
已知tan(α+π/4）=-1/2,π/2
答
tan(α+π/4）=-1/2
(tanα+tanπ/4)/(1-tanαtanπ/4) = -1/2
(tanα+1)/(1-tanα) = -1/2
2tanα+2 = -1+tanα
tanα = -3
π/2