诱导公式sin(-a)=-sin(a) cos(-a)=cos(a) sin(pi/2-a)=cos(a) cos(pi/2-a)=sin(a) sin(pi/2+a)=cos(a) cos(pi/2+a)=-sin(a) sin(pi-a)=sin(a) cos(pi-a)=-cos(a) sin(pi+a)=-sin(a) cos(pi+a)=-cos(a)tgA=tanA=sinA/cosA 两角和与差的三角函数 sin(a+b)=sin(a)cos(b)+cos(α)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(a-b)=cos(a)cos(b)+sin(a)sin(b) tan(a+b)=(tan(a)+tan(b))/(1-tan(a)tan(b)) tan(a-b)=(tan(a)-tan(b))/(1+tan(a)tan(b)) 三角函数和差化积公式 sin(a)+sin(b)=2sin((a+b)/2)cos((a-b)/2) sin(a)?sin(b)=2cos((a+b)/2)sin((a-b)/2)cos(a)+cos(b)=2cos((a+b)/2)cos((a-b)/2) cos(a)-cos(b)=-2sin((a+b)/2)sin((a-b)/2) 积化和差公式 sin(a)sin(b)=-1/2*[cos(a+b)-cos(a-b)] cos(a)cos(b)=1/2*[cos(a+b)+cos(a-b)] sin(a)cos(b)=1/2*[sin(a+b)+sin(a-b)] 二倍角公式 sin(2a)=2sin(a)cos(a) cos(2a)=cos^2(a)-sin^2(a)=2cos^2(a)-1=1-2sin^2(a) 半角公式 sin^2(a/2)=(1-cos(a))/2 cos^2(a/2)=(1+cos(a))/2 tan(a/2)=(1-cos(a))/sin(a)=sin(a)/(1+cos(a)) 万能公式 (2tan(a/2))/(1+tan^2(a/2))cos(a)= (1-tan^2(a/2))/(1+tan^2(a/2)) (2tan(a/2))/(1-tan^2(a/2))其它公式 a*sin(a)+b*cos(a)=sqrt(a^2+b^2)sin(a+c) [其中,tan(c)=b/a] a*sin(a)-b*cos(a)=sqrt(a^2+b^2)cos(a-c)[其中,tan(c)=a/b] 1+sin(a)=(sin(a/2)+cos(a/2))^2 1-sin(a)=(sin(a/2)-cos(a/2))^2 其他非重点三角函数 csc(a)=1/sin(a) sec(a)=1/cos(a) 双曲函数 sinh(a)=(e^a-e^(-a))/2 cosh(a)=(e^a+e^(-a))/2 tgh(a)=sinh(a)/cosh(a)