I
isnt000


Trong tam giác ABC,
C/M :
sin A = sin (B + C)
cos A/2 = sin (B + C)/2
tan A = - tan (B + C)
thanks trc'
C/M :
sin A = sin (B + C)
cos A/2 = sin (B + C)/2
tan A = - tan (B + C)
thanks trc'
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