tan15°+tan30°+tan15°xtan30° =tan（45°-30°）（1+tan30°）+tan30° =[（tan45°-tan30°）/（1+tan45°tan30°）]x（1+tan30°）+tan30° =[(1-√3/3)/(1+√3/3)]x (1+√3/3)+√3/3 =1-√3/3+√3/3 =1 ...