cos(x-π/2)=cos(π/2-x)=cosx=1/5 【角x是第二象限角?】
cos(x-π/2)=cos(π/2-x)=cosx=-1/5
则:sin(π+x)cos(π-x)tan(π-x)/tan(π+x)cos(3π/2+x)
=[(-sinx)(-cosx)(-tanx)]/[(tanx)(-sinx)]
=[sin²x]/[sin²x/cosx]
=cosx
=-1/5
cos(x-π/2)=cos(π/2-x)=cosx=1/5 【角x是第二象限角?】
cos(x-π/2)=cos(π/2-x)=cosx=-1/5
则:sin(π+x)cos(π-x)tan(π-x)/tan(π+x)cos(3π/2+x)
=[(-sinx)(-cosx)(-tanx)]/[(tanx)(-sinx)]
=[sin²x]/[sin²x/cosx]
=cosx
=-1/5