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sin(A+B)=sinAcosB+cosAsinB sin(A-B)=sinAcosB-sinBcosA
cos(A+B)=cosAcosB-sinAsinB cos(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)
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tan2A=2tanA/(1-tan2A) ctg2A=(ctg2A-1)/2ctga
cos2a=cos2a-sin2a=2cos2a-1=1-2sin2a
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sin(A/2)=â((1-cosA)/2) sin(A/2)=-â((1-cosA)/2)
cos(A/2)=â((1+cosA)/2) cos(A/2)=-â((1+cosA)/2)
tan(A/2)=â((1-cosA)/((1+cosA)) tan(A/2)=-â((1-cosA)/((1+cosA))
ctg(A/2)=â((1+cosA)/((1-cosA)) ctg(A/2)=-â((1+cosA)/((1-cosA))
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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)/2 cosA+cosB=2cos((A+B)/2)sin((A-B)/2)
tanA+tanB=sin(A+B)/cosAcosB tanA-tanB=sin(A-B)/cosAcosB
ctgA+ctgBsin(A+B)/sinAsinB -ctgA+ctgBsin(A+B)/sinAsinB
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1+2+3+4+5+6+7+8+9+â¦+n=n(n+1)/2 1+3+5+7+9+11+13+15+â¦+(2n-1)=n2
2+4+6+8+10+12+14+â¦+(2n)=n(n+1) 12+22+32+42+52+62+72+82+â¦+n2=n(n+1)(2n+1)/6
13+23+33+43+53+63+â¦n3=n2(n+1)2/4 1*2+2*3+3*4+4*5+5*6+6*7+â¦+n(n+1)=n(n+1)(n+2)/3
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ï¼sin^2ï¼x=1-cos2x/2
ï¼cos^2ï¼x=i=cos2x/2
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令tan(a/2)=t
sina=2t/(1+t^2)
cosa=(1-t^2)/(1+t^2)
tana=2t/(1-t^2)
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