求证-2sin αcos α+1/1-2cos*2α=tan α-1/tan α+1
问题描述：
求证-2sin αcos α+1/1-2cos*2α=tan α-1/tan α+1
答
证：(-2sinαcosα+1)/(1-2cos²α)=(sinα-cosα)²/(sin²α-cos²α)=(sinα-cosα)²/[(sinα+cosα)(sinα-cosα)]=(sinα-cosα)/(sinα+cosα)=(tanα-1)/(tanα+1)