三角函数基本公式 常用的三角函数公式
1.两角和差公式:sin (a b) = sinacosb cosasinb，cos(A+B) = cosAcosB-sinAsinB，cos(A-B) = cosAcosB+sinAsinB，tan (a+b) = (tana+tanb)/(
2.和差积公式:Sina+sinb = 2s in((a+b)/2)cos((a-b)/2)，Sina-sinb = 2cos((a+b)/2)sin((a-b)/2)，COSA+COSB。
3.乘积的和差公式:Sina sinb =-1/2[cos(a+b)-cos(a-b)]，cosa cosb = 1/2[cos(a+b)+cos(a-b)]，sinacosb = 1/2 [sin (a+b
4.角度加倍公式:sin2A=2sinAcosA，COS2A = COSA 2-SINA 2 = 1-2 SINA 2 = 2 COSA 2-1，TAN2A = (2TANA)/(1-TANA 2)
5.幂递减公式:sin 2 (α) = (1-cos (2α))/2，2cos 2 (α) = (1+cos (2α))/2，tan 2 (α) = (1-cos (2α))/(1+cos)
