tan(x+y)tan(x-y)=sin^2x-sin^2y/cos^2x-sin^2y 顺便问一下. tan,sin,

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tan(x+y)tan(x-y)=sin^2x-sin^2y/cos^2x-sin^2y 顺便问一下. tan,sin,cos是什么意思?

tan,正切；sin,正弦；cos,余弦
tan(x+y)tan(x-y)
=sin(x+y)/cos(x+y) * sin(x-y)/cos(x-y)
=sin(x+y)sin(x-y) / [cos(x+y)cos(x-y)]
=(sinxcosy+cosxsiny)(sinxcosy-cosxsiny) / [(cosxcosy-sinxsiny)(cosxcosy+sinxsiny)]
=[(sinxcosy)^2-(cosxsiny)^2] / [(cosxcosy)^2-(sinxsiny)^2]

tan(x+y)tan(x-y)=sin^2x-sin^2y/cos^2x-sin^2y 顺便问一下. tan,sin, 请问怎么证明sinX+sin(X+Y)+sin(X+2Y)/cosX+cos(X+Y)+cos(X+2Y)=tan(X+ 用matlab绘制y=tan(sin(x^2)) 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x sin（x+y)=1\2,sin(x—y）=1\3,求[tan（x+y）-tanx-tany]\[tany的平方tan（ 3sinX=sin(2X+Y) 求证：tan(X+Y)=2tanX 已知：3sinY=sin(2X+Y),求证tan(X+Y)=2tanX 已知5siny=sin(2x+y),求证:tan(x+y)=3/2tanx 已知sin(x+y)=1,求证：tan(2x+y)+tany=0 已知sin（x+y）=1,求证：tan（2x+3y）=tany sin(x+y)=1,则tan(2x+y)+tany= 已知sin(x+y)=1,求证:tan(2x+y)+tany=0