[sin(3pi/10)sin(pi/10)]/[sin(3pi/10)-sin9pi/10)]在线等

化简：sin(2pi-a)sin(pi+a)cos(-pi-a)/sin(3pi-a)cos(pi-a) sin(11*pi/3)=? 三角函数恒等变形证明sin( pi/3 ) + sin( 2*pi/3) + ...+ sin( n * pi/3)= 化简间sin（a-2pi)cos(a+pi）tan(a-99pi)cos(pi-a)sin(3pi-a)sin（-a-p tana=2求sin(pi-a)cos(2pi-a)sin(-a+3pi/2)/tan(-a-pi)sin(-pi-a) sin(3x+pi/3)的周期 log((sin(5))^2)-3+pi=? log((sin(30))^2)-3+pi= 求 log((sin(5))^2)-3+pi 证明sin(pi/n)*sin(2pi/n)*sin(3pi/n)*…sin((n-1)pi/n)=n/(2^(n-1) matlab求sin(pi) sin(pi/12)=?