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问题: 高一数学

化简根号下[(1+sinα)/(1-sina)]-根号下[(1-sinα)/(1+sinα)],其中α为第二象限角

解答:

[(1+sinα)/(1-sina)]-根号下[(1-sinα)/(1+sinα)]=
[(1+sinα)^2/(1-sina)(1+sinα)]-
根号下[(1-sinα)^2/(1+sinα)(1-sinα)]=
[(1+sinα)^2/(cosα)^2]-
根号下[(1-sinα)^2/(cosα)^2]=
(1+sinα)/(-cosα)-(1-sinα)/(-cosα)=
[(-1-sinα)+(1-sinα)]/cosα=
-2sinα/cosα=
-2tanα