sin平方a减cos平方a等于什么，过程谢谢 sin四次方a减cos四次方a为什么等于sin平方a减cos...
sin\u5e73\u65b9a\u51cf\u53bbcos\u5e73\u65b9a\u7b49\u4e8e?sin^2a-cos^2a
=-(cos^2-sin^2)
=-cos(2a)
\u89e3\u5982\u4e0b\u56fe\u6240\u793a
sin²α-cos²α=-(cos²α-sin²α)=-（（1+cos2α）/2-（1-cos2α)/2）sin²α）＝-cos2α
绛旓細sin²伪-cos²伪=-(cos²伪-sin²伪)=-cos2伪
绛旓細浜屽嶈鍏紡锛cos2a =2(cosa)^2-1 =1-2(sina)^2 =(sina)^2+(cosa)^2-2(sina)^2 =(cosa)^2-(sina)^2 =-[(sina)^2-(cosa)^2].
绛旓細=-(cos^2-sin^2)=-cos(2a)
绛旓細cos²a=1/10;sin²a=9/10;鍒檚in骞虫柟a-cos骞虫柟a=9/10-1/10=8/10=4/5;鎮ㄥソ锛屽緢楂樺叴涓烘偍瑙ｇ瓟锛宻kyhunter002涓烘偍绛旂枒瑙ｆ儜 濡傛灉鏈鏈変粈涔堜笉鏄庣櫧鍙互杩介棶锛屽鏋滄弧鎰忚寰楅噰绾 濡傛灉鏈夊叾浠栭棶棰樿閲囩撼鏈鍚庡彟鍙戠偣鍑诲悜鎴戞眰鍔╋紝绛旈涓嶆槗锛岃璋呰В锛岃阿璋傜瀛︿範杩涙 ...
绛旓細绛変簬1-2cos^2鎴栬2sin^2-1銆俿ina^2+cos^2=1锛宻in^2-cos^2 =锛1-cos^2锛-cos^2 =1-2cos^2 鎴杝in^2-cos^2 =sin^2-锛1-sin^2锛=sin^2-1+sin^2 =2sin^2-1
绛旓細cosa+sina=1/5 鎵浠ユ湁锛(cosa+sina)^2=1/25鍗筹細1+2sinacosa=1/25 寰楋細sin2a=-24/25cos2a=卤鈭歔1-(sin2a)^2]=卤7/25sin骞虫柟a鍑廲os骞虫柟a=-cos2a=卤7/25
绛旓細2x+y/3=1 x+3y/5=1 鎵浠2x+y=3 (1)x+3y=5 (2)(1)脳3-(2)6x+3y-x-3y=9-5 5x=4 x=4/5 y=3-2x=3/5 3锛坅+1)
绛旓細cos2a=cos2a-sin2a锛岃繖閲宎=伪/2銆傚睘浜庡嶈鍏紡銆俢os2伪/2-sin2伪/2=cosa/2cosa/2-sina/2sina/2=cos(a/2+a/2)=cosa銆傚嶈鍏紡锛屾槸涓夎鍑芥暟涓潪甯稿疄鐢ㄧ殑涓绫诲叕寮忋傚氨鏄妸浜屽嶈鐨勪笁瑙掑嚱鏁扮敤鏈鐨勪笁瑙掑嚱鏁拌〃绀哄嚭鏉ャ傚湪璁＄畻涓彲浠ョ敤鏉ュ寲绠璁＄畻寮忋佸噺灏戞眰涓夎鍑芥暟鐨勬鏁帮紝鍦ㄥ伐绋嬩腑涔熸湁骞挎硾鐨...
绛旓細瑙ｅ涓嬪浘鎵绀
绛旓細鍙敤浣欏鸡鐨勪簩鍊嶈鍏紡璁＄畻锛sinx骞虫柟-cosx骞虫柟 =sin²x-cos²x =-cos2x
