sin2x等于什么
=2sinxcosx这是个公式,证明如下
sin2x=sin（x+x)
=sinxcosx+sinxcosx
=2sinxcosx
绛旓細鍏充簬sin2x绛変簬浠涔鐢╟os琛ㄧず锛宻in2x绛変簬浠涔堣繖涓緢澶氫汉杩樹笉鐭ラ亾锛屼粖澶╂潵涓哄ぇ瀹惰В绛斾互涓婄殑闂锛岀幇鍦ㄨ鎴戜滑涓璧锋潵鐪嬬湅鍚э紒1銆乻in2x=2sinxcosx杩欏叾瀹炴槸鐢变袱瑙掑拰鐨勬寮﹀叕寮忥紝鐢眘in锛坸+y锛=sinxcosy+cosxsiny 寰楀埌銆2銆佹澶,杩樻湁鍑犱釜涓夎鎭掔瓑寮忥細cos锛坸-y锛=cosxcosy+sinxsinysin锛坸-y锛=sinxcosy-cosx...
绛旓細姝ｅ鸡鍑芥暟sin2x鏄竴涓父瑙佺殑鏁板鏈锛屽畠琛ㄧず鐨勬槸褰搙鍦ㄧ壒瀹氬懆鏈熷唴鍙樺寲鏃讹紝璇ュ嚱鏁扮殑鐗瑰畾鍙樺寲銆俿in2x鐨勫叕寮忓彲浠ラ氳繃涓绯诲垪鐨勬暟瀛﹁繍绠楀緱鍑猴紝鍏跺叿浣撳叕寮忎负sin(2x)=sin(x+x)銆傝繖涓叕寮忓湪璁稿绉戝鍜屽伐绋嬮鍩熼兘鏈夊箍娉涚殑搴旂敤锛屽鎸姩鍒嗘瀽銆佺數姘斿伐绋嬨佺墿鐞嗗寲瀛︾瓑銆俿in2x鐨勫煎彇鍐充簬x鐨勫彇鍊煎拰瑙掑害锛屽畠鍙兘鍦-1鍒...
绛旓細濡傛灉X鏄竴涓搴︾殑璇濓紝閭ｄ箞瀹冪殑鍘熷叕寮忔槸锛歴in锛圶+Y锛=sinXcosY+cosXsinY 浠=Y 閭ｄ箞锛sin2X=2sinXcosX
绛旓細sin2x=2sinxcosx sin4x=2sin2xcos2x 濡傛灉鎰挎剰锛岃繕鍙互缁х画鍖栦负x鐨勪笁瑙掑嚱鏁 娉ㄦ剰鍊嶈鍏紡涓殑瑙掔殑鍊嶆暟鏄浉瀵圭殑锛4鏄2鐨2鍊嶏紝1鏄1/2鐨勪簩鍊嶃
绛旓細cos2x绛変簬1-2*(sinX)^2銆俢os2x灞炰簬涓夎鍑芥暟涓殑浜屽嶈銆傛帹瀵艰繃绋嬶細cos2X銆=(cosX)^2-(sinX)^2銆=2*(cosX)^2-1銆=1-2*(sinX)^2銆傚悓瑙掍笁瑙掑嚱鏁扮殑鍩烘湰鍏崇郴寮忥細鍊掓暟鍏崇郴锛歵an伪路cot伪锛1銆sin伪路csc伪锛1銆乧os伪路sec伪锛1銆傚晢鐨勫叧绯伙細sin伪锛廲os伪锛漷an伪锛漵ec伪锛廲sc伪銆乧os伪锛...
绛旓細绛変环鏃犵┓灏忥紝sin2x~2x
绛旓細sin^2x宸茬粡鏄渶绠鐨勪簡涓嶉渶瑕佸寲绠銆傚鏋sin2x涓殑2涓嶆槸骞虫柟鑰屾槸鎸2x锛屽垯鍙牴鎹叕寮忓緱sin2x=2sinx•cosx銆1+cos2x锛氬叾涓璫os2x=2cos²x-1锛屾墍浠1+cos2x=1+2cos²x-1=2cos²x銆
绛旓細2sinxcosx
绛旓細sin2x=2sinxcosx锛(sin2x)/2=sinxcosx锛屽彧鏈塩osx=1鏃讹紝sin2x鎵绛変簬sinx銆
绛旓細sin2x鐨勮瀵煎叕寮忔槸sin2x = 2sinx*cosx銆傝繖涓叕寮忔槸鍩轰簬涓夎鍑芥暟鐨勫拰宸叕寮忓拰鍊嶈鍏紡鎺ㄥ鍑烘潵鐨勩傝繖涓叕寮忕殑鎰忎箟鍦ㄤ簬锛屽畠鑳藉皢涓涓惈鏈2鍊嶈鐨勪笁瑙掑嚱鏁拌〃杈惧紡杞寲涓哄惈鏈夊崟涓搴︾殑涓夎鍑芥暟琛ㄨ揪寮忥紝浠庤屼娇寰楄绠楀彉寰楁洿涓虹畝渚裤備緥濡傦紝濡傛灉鎴戜滑鎯虫眰sin(2x)鐨勫硷紝鎴戜滑鍙互鐢ㄨ繖涓叕寮忓皢鍏惰浆鍖栦负鍚湁sinx鍜宑osx鐨...
