1、1。诱导公式sin(a)=sin(a) cos(a)=cos(a) sin(2a)=cos(a) cos(2-a)=sin(a) sin(2+a)=cos(a) cos(2+a)=sin(a) sin(-a)=sin(a) cos(a)=cos(a) sin(+a)=sin(a) cos(+a)=cos(a) tgA=tanA=sinAcosA 2。两角和与差的三角函数sin(a+b)=sin(a)cos(b)+cos()sin(b) cos(a+b)=cos(a)cos(b)sin(a)sin(b) sin(a-b)=sin(a)cos(b)-cos(a)sin(b) cos(ab)=cos
2、(a)cos(b)+sin(a)sin(b) tan(a+b)=tan(a)+tan(b)/1tan(a)tan(b)tan(ab)=tan(a)-tan(b)/1+tan(a)tan(b)3。和差化积公式sin(a)+sin(b)=2sin((a+b)/2)cos(ab)/2) sin(a)sin(b)=2cos((a+b)/2)sin(a-b)/2) cos(a)+cos(b)=2cos((a+b)/2)cos(ab)/2) cos(a)cos(b)=2sin(a+b)/2)sin(ab)/2) 4.积化和差公式 (上面公式反过来就得到了) sin(a)sin(b)=1/2* cos(a+
3、b)cos(ab) cos(a)cos(b)=1/2* cos(a+b)+cos(a-b) sin(a)cos(b)=1/2 sin(a+b)+sin(ab) cos(a)sin(b)=1/2* sin(a+b)sin(ab)5.二倍角公式sin(2a)=2sin(a)cos(a) cos(2a)=cos2(a)-sin2(a)=2cos2(a)-1=12sin2(a) 6。半角公式2sin2(a/2)=1-cos(a) 2cos2(a/2)=1+cos(a) tan(a/2)=1-cos(a)/sin(a)=sina/1+cos(a) tan2(a/2)= 1-cos(a)/1+cos(a)
4、7.万能公式sin(a)=2tan(a/2)/1+tan2(a/2)cos(a)=1tan2(a/2)/1+tan2(a/2)tan(a)=2tan(a/2)/1-tan2(a/2)8。其它公式(推导出来的) asin(a)+b*cos(a)=sin(a+c) 其中 tan(c)=b/a a*sin(a)-b*cos(a)=cos(ac) 其中 tan(c)=a/b 1+sin(a)=(sin(a/2)+cos(a/2)21- sin(a)=(sin(a/2)cos(a/2))2三、正弦定理: a/sinA=b/sinB=c/sinC=2R 其中R是三角形外接圆半径正弦定理可以解决下列三角问题:已知两角和任一边,求其它两边和一角。已知两边和其中一边的对角,求另一边的对角.公式的变形:a:b:c=sinA:sinB:sinC a=k*sinA, b=k*sinB, c=k*sinC 四、余弦定理:a2=b2+c22bccosA b2=a2+c22accosB c2=a2+b22abcosC 赞同