问题描述: 求证:tan(x/2+π/4)+tan(x/2-π/4)=2tanx 1个回答 分类:数学 2014-11-10 问题解答: 我来补答 证明:左边=[tan(x/2) +tan(π/4)]/[1 - tan(x/2)tan(π/4)] + [tan(x/2) - tan(π/4)]/[1 + tan(x/2)tan(π/4)]=[tan(x/2) +1 ]/[1 - tan(x/2)] + [tan(x/2) - 1]/[1 + tan(x/2)] (对该式通分后得到下式)={[tan(x/2) +1 ]² - [tan(x/2) -1 ]²/[1- tan²(x/2)]=4tan(x/2)/[1- tan²(x/2)] (倍角(半角)公式得到下式)=2tanx 展开全文阅读