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¡÷ABC,sinA=cosB=tanC,Çócos^3A+cos^2A - cosA?
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1 Á½½ÇºÍ¹«Ê½sin(A+B) = sinAcosB+cosAsinBsin(A-B) = sinAcosB-cosAsinBcos(A+B) = cosAcosB-sinAsinBcos(A-B) = cosAcosB+sinAsinB 2 ...
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tan(A/2)=(1-cosA)/sinA=sinA/(1+cosA); cot(A/2)=sinA/(1-cosA)=(1+cosA)/sinA. sin^2(a/2)=(1-cos(a))/2 cos^2(a/2)=(1+cos(a...
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...tanC=sinA+sinB/cosA+cosB,sin(B - A)=cosC.(1).ÇóA...
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