tan45=tan(19+26)=(tan19+tan26)/(1-tan19*tan26)=1
tan19+tan26=1-tan19*tan26
所以
tan19+tan26+tan19*tan26=1 选A为什么tan19+tan26=1-tan19*tan26我晕哦(tan19+tan26)/(1-tan19*tan26)=1两边乘(1-tan19*tan26)就得到嘛