小学数学公式：和差化积
<p>和差化积</p><p>2sinAcosB=sin(A+B)+sin(A-B) 2cosAsinB=sin(A+B)-sin(A-B)</p><p>2cosAcosB=cos(A+B)-sin(A-B) -2sinAsinB=cos(A+B)-cos(A-B)</p><p>sinA+sinB=2sin((A+B)/2)cos((A-B)/2 cosA+cosB=2cos((A+B)/2)sin((A-B)/2)</p><p>tanA+tanB=sin(A+B)/cosAcosB tanA-tanB=sin(A-B)/cosAcosB</p><p>ctgA+ctgBsin(A+B)/sinAsinB -ctgA+ctgBsin(A+B)/sinAsinB</p>
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