椭圆公式知识点篇三
两角和公式
sin(A+B)=sinAcosB+cosAsinBsin(A—B)=sinAcosB—sinBcosA
cos(A+B)=cosAcosB—sinAsinBcos(A—B)=cosAcosB+sinAsinB
tan(A+B)=(tanA+tanB)/(1—tanAtanB)tan(A—B)=(tanA—tanB)/(1+tanAtanB)
ctg(A+B)=(ctgActgB—1)/(ctgB+ctgA)ctg(A—B)=(ctgActgB+1)/(ctgB—ctgA)
倍角公式
tan2A=2tanA/(1—tan2A)ctg2A=(ctg2A—1)/2ctga
cos2a=cos2a—sin2a=2cos2a—1=1—2sin2a
半角公式
sin(A/2)=√((1—cosA)/2)sin(A/2)=—√((1—cosA)/2)
cos(A/2)=√((1+cosA)/2)cos(A/2)=—√((1+cosA)/2)
tan(A/2)=√((1—cosA)/((1+cosA))tan(A/2)=—√((1—cosA)/((1+cosA))
ctg(A/2)=√((1+cosA)/((1—cosA))ctg(A/2)=—√((1+cosA)/((1—cosA))
和差化积
2sinAcosB=sin(A+B)+sin(A—B)2cosAsinB=sin(A+B)—sin(A—B)
2cosAcosB=cos(A+B)—sin(A—B)—2sinAsinB=cos(A+B)—cos(A—B)
sinA+sinB=2sin((A+B)/2)cos((A—B)/2cosA+cosB=2cos((A+B)/2)sin((A—B)/2)
tanA+tanB=sin(A+B)/cosAcosBtanA—tanB=sin(A—B)/cosAcosB
ctgA+ctgBsin(A+B)/sinAsinB—ctgA+ctgBsin(A+B)/sinAsinB
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