cos(x-90)=sinx

这是三角函数诱导公式之一,是恒等式,也可以用三角函数和差化积进行展开,
cos(x-90°)=cosxcos90°+sinxsin90°=cosx*0+sinx*1=sinx.

cos(x-90)=sinx
绛旓細cos(x-90掳)=cosxcos90掳+sinxsin90掳=cosx*0+sinx*1=sinx.

cosx-90掳绛変簬sinx鍚?
绛旓細cosx-90掳绛変簬sinx cosx=cos(-X)鏁cos(x-90)=cos(90-x)=sinx 濂囧彉鍋朵笉鍙橈紝绗﹀彿鐪嬭薄闄愶細濂囧彉鍋朵笉鍙橈細鍏朵腑鐨勫鍋舵槸鎸囅/2鐨勫鍋舵暟鍊嶏紝鍙樹笌涓嶅彉鏄寚涓夎鍑芥暟鍚嶇О鐨勫彉鍖栵紝鑻ュ彉锛屽垯鏄寮﹀彉浣欏鸡锛屾鍒囧彉浣欏垏銆傜鍙风湅璞￠檺锛氭牴鎹鐨勮寖鍥翠互鍙婁笁瑙掑嚱鏁板湪鍝釜璞￠檺鐨勬璐燂紝鏉ュ垽鏂柊涓夎鍑芥暟鐨勭鍙枫

sin(x)=cos(x-90搴) 杩欎釜瀵逛笉瀵瑰晩
绛旓細鍥犱负cos(-x)=cosx 鎵浠sinx=cos(90-x)=cos[-(90-x)]=cos(x-90)

sin涓cos鐨勮浆鎹
绛旓細鍥犱负sinX=cos(90-X)鎵浠inX=cos(X-90)鎵浠inX=cos(X+?)涓殑锛= 360K-90锛屽叾涓璌涓烘暣鏁 濡傦紵= -90銆270...

璋佽兘鍒椾妇涓涓sinx鍜cosx浜掓崲鐨勪笁瑙掑嚱鏁扮殑鍏紡?
绛旓細cosx=sin(90-x)(x<=90)=sin(x-90)(x>90)

cos(90-x)绛夋柤浠楹
绛旓細濂囧彉鍋朵笉鍙橈紝cos鍑芥暟灏卞彉鎴恠in鍑芥暟锛岀鍙风湅璞￠檺锛屾妸X褰撳仛绗竴璞￠檺鐨勮锛90-X涔熸槸閿愯锛岄偅涔cos锛90-X锛灏辨槸姝ｇ殑锛岀瓑浜sinX

涓轰粈涔sinX=cos(90掳-X)
绛旓細鍋囪鐩磋涓夎褰BC涓,瑙扖涓虹洿瑙.瑙払涓篨,閭ｈA灏辨槸90-X.sinX=AC/AB cos(90-X)=cos瑙扖AB=AC/AB 鎵浠ヤ袱涓浉绛 浣犺嚜宸辩敾涓浘

sinx=cos(90-x)杩樻槸cosx=sin(90-x)!!!涓鏍峰悧
绛旓細閮芥垚绔嬶紝50掳鍜40掳浜掍负浣欒

sin鍜cos鐨勫叧绯??
绛旓細绠鍗曞湴璇村氨鏄浉宸90搴︼紝sinx=cos(90搴-x)鏈夊彞鍙ｈ瘈锛氬熀鍙樺伓涓嶅彉锛岀鍙风湅璞￠檺 鍩恒佸伓鏄寚90鐨勫熀鏁板嶅拰鍋舵暟鍊嶏紝鍙樸佷笉鍙樻槸鎸噑in锛宑os鏄惁鍙樺寲锛岀鍙锋槸鎸噑in锛宑os鐨勬璐 濡sinX=cos(X+270) 涓紝270鏄90鐨勫熀鏁板嶏紝鏁卌os鍙樻垚sin锛屾妸X鐪嬫垚涓閿愯锛屼竴閿愯鍔270鏄鍥涜薄闄愯锛屽湪cos涓鍥涜薄闄愯涓...

sinx=(cosx90-x)
绛旓細sinx=cos(90掳-x):瀵 cosx=sin(90掳-x):瀵 sin40掳=cos50掳: 瀵 cos40掳=sin50掳:瀵

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