tan75°/(1-tan² 75°)
=(1/2)*2tan75°/(1-tan² 75°)
=(1/2)*tan150°
=（1/2)*(-tan30°)
=-(1/2)*(√3)/3
=(√3)/6
tan75/1-tan^275等于多少
tan75°/(1-tan² 75°)
=(1/2)*2tan75°/(1-tan² 75°)
=(1/2)*tan150°
=（1/2)*(-tan30°)
=-(1/2)*(√3)/3
=(√3)/6