V2

Cos[θ + π] = -Cos[θ]

Sin[θ + π] = -Sin[θ]

V2x == -Dv2 Cos[θ]

V2y == -Dv2 Sin[θ]

Vx == -Dv Sin[θ]

Vy = Dv Cos[θ]

By == (V2y - Vy)/(V2x - Vx) (-Bx - Vx) + Vy

DvH2/Hight == ((V2x - Vx)^2 + (V2y - Vy)^2)^(1/2)/((-Bx - Vx)^2 + (By - Vy)^2)^(1/2)

Solve