cos(9π/4)+tan(-7π/6)+sin(21π)=

问题描述:

cos(9π/4)+tan(-7π/6)+sin(21π)=

cos(9π/4)+tan(-7π/6)+sin(21π)
=cosπ/4-tan(π/6)+0
=√2/2-√3/3sin21π怎么化?sin(21π)=sin(20π+π)=sinπ=0