用和角来算
因为tan(a+β)=2/5,tan(β-π/4)=1/4
a+β-(β-π/4)=a+π/4
所以tan(a+π/4)=[tan(a+β)-tan(β-π/4)]/[1+tan(a+β)tan(β-π/4)]=3/22
tan(a+β)=tan(a+4分之π+β-4分之π)
=[tan(β-4分之π)+tan(a+4分之π)]/[1-tan(β-4分之π)*tan(a+4分之π)]
=[1/4+tan(a+4分之π)]/[1-1/4*tan(a+4分之π)]
=2/5
tan(a+4分之π)=1/6
tan(α+π/4)={tan[(α+β)-tan(β-Π/4)]}/ [1+tan(a+β)tan(β-4分之π)] =(2/5+1/4)/(1-2/5 * 1/4)