def write_v_dt(self):
    brace = Brace(self.nose_lines, DOWN, buff=0)
    equation = TexMobject('ds', '=', 'v(t)', 'dt')
    equation.next_to(brace, DOWN, SMALL_BUFF, LEFT)
    equation.set_color_by_tex('ds', DISTANCE_COLOR)
    equation.set_color_by_tex('dt', TIME_COLOR)
    negative = TextMobject('Negative')
    negative.set_color(RED)
    negative.next_to(equation.get_corner((UP + RIGHT)), UP, LARGE_BUFF)
    (ds_arrow, v_arrow) = arrows = VGroup(*[Arrow(negative.get_bottom(), equation.get_part_by_tex(tex).get_top(), color=RED) for tex in ('ds', 'v(t)')])
    self.play(GrowFromCenter(brace), Write(equation))
    self.wait()
    self.play(FadeIn(negative))
    self.play(ShowCreation(v_arrow))
    self.wait(2)
    self.play(ReplacementTransform(v_arrow.copy(), ds_arrow))
    self.wait(2)
    self.ds_equation = equation
    self.negative_word = negative
    self.negative_word_arrows = arrows
def write_v_dt(self):
    brace = Brace(self.nose_lines, DOWN, buff=0)
    equation = TexMobject('ds', '=', 'v(t)', 'dt')
    equation.next_to(brace, DOWN, SMALL_BUFF, LEFT)
    equation.set_color_by_tex('ds', DISTANCE_COLOR)
    equation.set_color_by_tex('dt', TIME_COLOR)
    negative = TextMobject('Negative')
    negative.set_color(RED)
    negative.next_to(equation.get_corner((UP + RIGHT)), UP, LARGE_BUFF)
    (ds_arrow, v_arrow) = arrows = VGroup(*[Arrow(negative.get_bottom(), equation.get_part_by_tex(tex).get_top(), color=RED) for tex in ('ds', 'v(t)')])
    self.play(GrowFromCenter(brace), Write(equation))
    self.wait()
    self.play(FadeIn(negative))
    self.play(ShowCreation(v_arrow))
    self.wait(2)
    self.play(ReplacementTransform(v_arrow.copy(), ds_arrow))
    self.wait(2)
    self.ds_equation = equation
    self.negative_word = negative
    self.negative_word_arrows = arrows