sin21°cos39°+cos21°sin39°=

(sin39° -sin21°)/(cos39°-cos21°) sin21°cos39°+cos21°sin39°= (sin24°cos6°-sin66°sin6°)/(sin21°cos39°-cos21°sin39°) 求sin39°-sin21°/cos39°-cos21°的值急需过程,谢谢! (sin24°cos6°-sin66°sin6°)/(sin21°cos39°-cos21°sin39°)化简后得 sin21°cos24°+cos21°sin24° sin21°cos81°-cos21°sin81°=? 求值sin21°cos24°+cos21°sin24°过程 求值sin21°cos24°+cos21°sin24°过程 sin21°cos9°+cos21°sin9°=? （cos^2 33°-cos^2 57°）／（sin21°－cos21°） sin21 cos21等于几?精确啊 cos39°cos9°+sin39°sin9°= cos51°cos9°-cos39°sin9°= 1.比大小：tan21°和tan31°；2.sin21°和cos21°；3.cos21°和cos22°遇到这样的题目该怎么解?2.把正整数1,2,3,4,5.按如下规律排列：12,3,4,5,6,7,8,9,10,11,12,13,14,15,.按此规律,可知第n行有多少个正整数?不只要 sin21度 cos21度 tan38度等于多少? sin21°cos81°-sin69°cos9° 求值：sin21°cos81°-sin69°cos9°