sinA+sinB=1/2,cosA+cosB=-2/3,求:tanA*tanB=?
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sinA+sinB=1/2,cosA+cosB=-2/3,求:tanA*tanB=?sinA+sinB=1/2,cosA+cosB=-2/3,求:tanA*tanB=?sinA+sinB=1/2,co
sinA+sinB=1/2,cosA+cosB=-2/3,求:tanA*tanB=?
sinA+sinB=1/2,cosA+cosB=-2/3,求:tanA*tanB=?
sinA+sinB=1/2,cosA+cosB=-2/3,求:tanA*tanB=?
(sinA+sinB)^2=1/4……(1)
(cosA+cosB)^2=4/9……(2)
(1)+(2),整理得
2+2(sinAsinB+cosAcosB)=25/36
sinAsinB+cosAcosB=-47/72
cos(A-B)=-47/72……(3)
sin(A-B)=±√{1-[cos(A-B)]^2}
(2)-(1),整理得
cos2A+cos2B+2cos(A+B)=7/36
2cos(A+B)cos(A-B)+2cos(A+B)=7/36
cos(A+B)=7/25……(4)
由(3)、(4)得出
sinAsinB=-0.466
cosAcosB=-0.186
tanA*tanB=2.503
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