sin7/5pai*cos(-11/6pai)+tan(-15/4pai)*tan7/5pai,计算得数,
问题描述：
sin7/5pai*cos(-11/6pai)+tan(-15/4pai)*tan7/5pai,计算得数,
答
sin(7/5π)cos(-11/6π)+tan(-15/4π)tan(7/5π)=sin(π+2/5π)cos(2π-1/6π)-tan(4π-1/4π)tan(π+2/5π) =-sin( 2/5π)cos(1/6π)+tan(1/4π)tan(2/5π)=-0.9511×0.8660+1×3.078≈-0.8237+3.078=2.2543