tan（90°-X）=？请给出答案和解释。谢谢喵~
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tan（90°-X）=cotx这是诱导公式
tan（90°-X）=
sin（90-x） / cos(90-x)
=
函数名变
cosx / sinx
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绛旓細30搴45搴60搴90搴︾殑浣欏鸡銆佹鍒囥佹寮︺佷綑鍒囨墍瀵瑰簲鐨勫煎鍥炬墍绀猴細
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绛旓細tan(45掳-x)=3 (tan45掳-tanx)/(1+tan45掳tanx)=3 (1-tanx)/(1+tanx)=3 1-tanx=3+3tanx 4tanx=-2 tanx=-0.5
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绛旓細鍥炵瓟锛氬洜涓 tan(90+x)搴 = cot[90-(90+x)]搴 = cot(-x)搴 = -cotx搴 = -1/tanx搴
绛旓細tan鐨勬墍鏈夊叕寮忔湁锛氬崐瑙掑叕寮忋tan(伪锛2)=sin伪锛忥紙1+cos伪锛夛紳(1-cos伪锛夛紡sin伪銆傚嶈鍏紡銆倀an2伪锛濓紙2tan伪锛夛紡(1-tan伪锛2)銆傞檷骞傚叕寮忋倀an^2(伪锛夛紳(1-cos(2伪锛/(1+cos(2伪锛夈備竾鑳藉叕寮忋倀an伪锛2tan(伪锛2)/銆備袱瑙掑拰涓庡樊鍏紡銆倀an(伪锛嬑诧級锛(tan伪锛媡an尾锛夛紡(1-tan...
绛旓細姣斿tan135掳= - tan(180掳-135掳)= -tan45掳 锛屼互姝ゆ硶璁綼锛90掳 tan a = -tan(180-a)锛佹湜閲囩撼锛岃阿璋紒
绛旓細sin(x+90)=cosxsin90+sinxcos90=cosx+0=cosx cos(x+90)=cosxcos90-sinxsin90=0-sinx=-sinx tan(x+90)=sin(x+90)/cos(x+90)=cosx/(-sinx)=-cotx 澶熻缁嗕簡鍚э紵
