sinA+sinB=1/4,cosA+cosB=1/3,求cos(A-B)的值和sin(A+B)的值

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sinA+sinB=1/4,cosA+cosB=1/3,求cos(A-B)的值和sin(A+B)的值sinA+sinB=1/4,cosA+cosB=1/3,求cos(A-B)的值和sin(A+B)的值

sinA+sinB=1/4,cosA+cosB=1/3,求cos(A-B)的值和sin(A+B)的值
sinA+sinB=1/4,cosA+cosB=1/3,求cos(A-B)的值和sin(A+B)的值

sinA+sinB=1/4,cosA+cosB=1/3,求cos(A-B)的值和sin(A+B)的值
cos(A-B)=cosAcosB+sinAsinB
(sinA+sinB)^2+(cosA+cosB)^2=sin^2A+2sinAsinB+sin^2B+cos^2A+2cosAcosB+cos^B=2+2cos(A-B)=1/9+1/16
cos(A-B)=-263/288
(sinA+sinB)(cosA+cosB)=sinAcosA+sinBcosB+sinAcosB+cosAsinB=cos(A-B)+sin(A+B)=1/12
sin(A+B)=287/288