已知sin(x+π)=4/5,且sinxcosx
问题描述：
已知sin(x+π)=4/5,且sinxcosx
答
sin(x+π)=4/5sin(x+π)=4/5sinx=-4/5∵sinxcosx0cosx=3/5tanx=-4/32sin(x-π)+tan(π-x)/4cos(x-3π)=-2sinx+tan(-x)/4cos(x-π)=-2sinx+tanx/4cosx=8/5+(-4/3)/(4*3/5)=8/5-5/9=47/45