因为tan b=1/3所以tan(2b)=2tanb /(1-tanbtanb)=3/4,
所以tan(a+2b)=(tan a +tan2b)/(1-tanatan2b),将tana = 1/7和tan2b=3/4代入其中,可得tan(a +2b )=1
因为tan b=1/3所以tan(2b)=2tanb /(1-tanbtanb)=3/4,
所以tan(a+2b)=(tan a +tan2b)/(1-tanatan2b),将tana = 1/7和tan2b=3/4代入其中,可得tan(a +2b )=1