Question

x趋向于1极限（x-1）tan派x/2

Answer 1

（x-1）tanπx/2

=[（x-1）sinπx/2]/cosπx/2

=[（x-1）sinπx/2]'/(cosπx/2)'

=[sinπx/2+(x-1)cosπx/2*π/2]/[-sinπx/2*π/2]

=-2/π ,x-->1