2015中考數(shù)學(xué)知識點復(fù)習(xí):和差化積

中考數(shù)學(xué)知識點復(fù)習(xí):和差化積
    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