在三角形ABC中,角A,B,C對邊分別爲a,b,c.証明:(a*2--b*2)/c*2=sin(A--B)/sinC
*爲平方的意思 網友廻答:
- )/2]/sin^2C=[sin(A B)*sin(A-B)]/sin^2C,
網友廻答:
- a/sinA=b/sinB=c/sinC=2R,a=sinA*2R,b=sinB*2R,c=sinC*2R,左邊有(a^2-b^2)/c^2=(sin^2A-sin^2B)/sin^2C=[(sinA sinB)(sinA-sinB)]/sin^2c=[2sin(A B)/2*cos(A-B)/2*2cos(A B)/2*sin(A-B)/2]/sin^2C=[sin(A B)*sin(A-...
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