Respuesta :

TheHero
sin2B = 2sinBCosB (double angle formula)

sin(B/2) = 1/2 - 1/2 Cos(B)

Pi to 3pi/2 -> 3rd quadrant

cosB-> negative , sinB negative

CosB = -5/13

sin2B = 2 * -5/13 * -12/13 = 120/169

sinB/2 = 1/2 - 1/2 * * -5/13 = 9/13

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