1-tanα/1+tanα=1-2sinαcosα/cos^2α-sin^2α求证啊
1个回答

1-sinα/cosα sin^2α+cos^2α-2sinαcosα

------------ = --------------------------

1+sinα/cosα cos^2α-sin^2α

1-sinα/cosα (sinα-cosα)^2

------------ = --------------------

1+sinα/cosα cos^2α-sin^2α

cosα-sinα (cosα-sinα)^2

------------ = --------------------

cosα+sinα (cosα-sinα)(cosα+sinα)

cosα-sinα (cosα-sinα)

------------ = --------------------

cosα+sinα (cosα+sinα)