有B=2A+B,或2A+B+B=180°
所以A=0或A+B=90°
sin(2A+B)=sin(A+B)cosA+cos(A+B)sinA=sinB
cos(2A+B)=sin(A+B)cosA-cos(A+B)sinA
1)当A=2K∏,K=0,1,2,.
tan(2A+B)=1
2）当A+B=2K∏+∏/2,K=0,1,2,3...
tan(2A+B)=1
所以tan(2A+B)=1