cos43/4π与sin(-21/5π)比大小

问题描述:

cos43/4π与sin(-21/5π)比大小

cos43/4π = cos3/4π=-sin1/4π
sin(-21/5π)=sin(-1/5π)=-sin(1/5π)
sin(1/5π)-sin(1/4π)
cos43/4π