求证:tan(x-π/4)=(sinx-cosx)/(sinx+cosx)

问题描述:

求证:tan(x-π/4)=(sinx-cosx)/(sinx+cosx)

原式=sin(x-π/4)/cos(x-π/4)=(sinxcosπ/4-cosxsinπ/4)/(cosxcosπ/4+sinxsinπ/4)=【√2/2(sinx-cosx)】/【√2/2(sinx+cosx)】=(sinx-cosx)/(sinx+cosx)=右式