求值：⑴sin(-19π/3)*cos(19π/6)
问题描述：
求值：⑴sin(-19π/3)*cos(19π/6)
⑵cos(-585°)/[sin(-330°)+tan495°]
已知log2sina=-1且a∈[0,2π）,求a的值
答
sin(-19π/3)*cos(19π/6)=-sin(19π/3)*cos(19π/6)=-sin(6π+π/3)*cos(3π+π/6)=-sin(π/3)*(-cosπ/6)=√3/2*√3/2=3/4cos(-585°)/[sin(-330°)+tan495°]=cos(-585°+720°)/[sin(-330°+360°)+tan(495°-54...