1式:sinAsinB+sinAcosB=sinC =sin(A+B)=sinAcosB+sinBcosA
得 sinAsinB=sinBcosA
所以sinA=cosA A=45
2式:sinB=-cos2c=sin(2C-90)
B=2c-90或B=180-(2C-90) 又B+C=135
解出B=60,C=75 B=0,C=135(舍)
1式:sinAsinB+sinAcosB=sinC =sin(A+B)=sinAcosB+sinBcosA
得 sinAsinB=sinBcosA
所以sinA=cosA A=45
2式:sinB=-cos2c=sin(2C-90)
B=2c-90或B=180-(2C-90) 又B+C=135
解出B=60,C=75 B=0,C=135(舍)