∵tan（x+87π）=tan（x+π+π7）=tan（x+π7）=t，∴sin(157π+x)+3cos(x−137π)sin(207π−x)−cos(x+227π)=sin(x+π7+2π)+3cos(x+π7−2π)sin(3π−π7−x)−cos(x+π7+3π)=sin(x+π7)+3cos(x+π7)sin(π7+x...