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1、欧阳音创编欧阳音创编2021.03.112021.03.11三角恒等变换所有公式时间：2021.03. 11创作：欧阳音两角和与差的三角函数:cos (a +3 )=cos a cossin (a +sin (ci-tan (a +tan (a -(J )=cos a coscoscos|3 +cos a s i nB )二仕an a +tan 0)/(1 -tan a tan J)B )二(tan a 一tan 0)/(1 +tan a tan p )二倍角公式:s i n (2 a)=2s i n a cos acos(2 a )=cos2(a)-sin2(a)=2cos2(a )-1=1
2、-2sin2(a)tan (2 a)=2tan a/l-tan2(a)三倍角公式：s i n3 a =3s i n a-4s i n3 ( a)cos3 a =4cos3 ( a)-3cos a半角公式：s i rT2 ( a /2) = (1-cos a ) /2欧阳音创编2021.03.11欧阳音创编2021.03.11欧阳音创编欧阳音创编2021.03.112021.03.11cos2 ( a /2) = (1 +cos a ) /2tan2 ( a /2) = (1 -cos a ) / (1 +cos a )tan( a /2) =sin a/(1 +cos a ) = (1 -co
3、s a )/sin a万能公式：半角的正弦、余弦和正切公式(降幕扩角公式)s i n a =2tan ( a /2)/l+tan2 ( a /2)cos a = 1-tan2 ( a /2) /1+tan2 ( a /2)tan a =2tan ( a/2)/1-tan2(a/2)积化和差公式：s i n a cos(3= (1 /2)sin(a + |3)+sin(a-p)cos a -sinP= (1 /2)sin(a + p)-sin(a-p)cos a cos3= (1/2)cos ( a + (3 ) +cos ( a - 3 )s in a sin(J=-(1/2) cos ( a + p )-cos ( a - (3)和差化积公式：s in a +s i n P =2s in (a + |3 )/2cos(a - P )/2 sin a-sin J =2cos ( a + J ) /2 s i n ( a - P ) /2 cos a +cos 3 =2cos ( a + 3 )/2 cos ( a - 卩)/2 cos a -cos (J 二一2s i n ( a + 3 ) /2 s i n ( a - p ) /2时间:2021.03.11创作：欧阳音欧阳音创编欧阳音创编2021.03.112021.03.11
