sin^3A+cos^3A=1,求sinA+cosA?
人气：395 ℃ 时间：2020-04-10 13:54:37
解答
sin^3A+cos^3A=1(sinA+cosA)(sin^2A-sinAcosA+cos^2A)=1(sinA+cosA)(1-sinAcosA)=1两边平方得：(sin^2A+2sinAcosA+cos^2A)*(1-sinAcosA)^2=1,(1+2sinAcosA)*(1-sinAcosA)^2=1,设m=sinAcosA,则(1+2m)*（1-m)^2=1,2m^3...
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