Ο Ευκλείδης Προτείνει…
ΕΥΚΛΕΙΔΗΣ Β’ 124 (2022) τ.4/1
Άσκηση 392
Θεωρούμε τρίγωνο ΑΒΓ και τα ύψη του . Αν
οι προβολές των Β και Γ στην ευθεία
να αποδείξετε ότι:
α. β.
Σταματιάδης Βαγγέλης – Ν. Ιωνία
Λύση
Ο Ευκλείδης Προτείνει…
ΕΥΚΛΕΙΔΗΣ Β’ 124 (2022) τ.4/1
Άσκηση 392
Θεωρούμε τρίγωνο ΑΒΓ και τα ύψη του . Αν
οι προβολές των Β και Γ στην ευθεία
να αποδείξετε ότι:
α. β.
Σταματιάδης Βαγγέλης – Ν. Ιωνία
Λύση
Συχνά ο θείος μου ο Βλαδίμηρος (όχι ο Πούτιν!) μου στέλνει ασκήσεις γεωμετρίας όπως η παρακάτω:
Σε τετράγωνο ΑΒΓΔ πλευράς 10 φέρνουμε τα μέσα Ε, Ζ δυο διαδοχικών πλευρών του (βλέπε σχήμα). Να υπολογιστεί το εμβαδόν του σκιαγραμμένου τετραπλεύρου.
Λύση
Θέμα 3 από το MATHEMATICAL GRAMMAR SCHOOL CUP- MATHEMATICS -29. June 2022.
Να βρείτε το τελευταίο ψηφίο του ΕΚΠ των αριθμών
Μια απόδειξη της πρότασης : εφ(a)εφ(b)+εφ(b)εφ(c)+εφ(c)εφ(a)=1 όταν a+b+c=π/2.
Το βίντεο με τα animations έγινε με το λογισμικό manim.
οδηγίες για την εγκατάσταση του λογισμικού Manim και για δημιουργία μαθηματικών animation εδώ Διαβάστε όλο το άρθρο »
Εγκατάσταση του Chocolatey:
Πρώτον, βεβαιωθείτε ότι χρησιμοποιείτε ένα τερματικό των Windows (PowerShell) με δικαιώματα διαχειριστή.
Με αυτό το PowerShell, και την εντολή Get-ExecutionPolicy
θα δούμε τι δικαιώματα έχουμε ώστε μετά να διασφαλίσετε ότι τα δικαιώματά μας δεν είναι περιορισμένα (Restricted).
Μια απόδειξη χωρίς λόγια για την πρόταση:
Το εμβαδόν ενός τριγώνου είναι ίσο με το γινόμενο της ακτίνας (r) του εγγεγραμμένου κύκλου του και της ημιπεριμέτρου του τριγώνου (s).
Το βίντεο έγινε με το λογισμικό Manim.
from manim import *
class CreateCircle(Scene):
def construct(self):
circle = Circle() # create a circle
circle.set_fill(PINK, opacity=0.5) # set the color and transparency
self.play(Create(circle)) # show the circle on screen
class HelloLaTeX(Scene):
def construct(self):
tex = Tex(r"\LaTeX", font_size=144)
self.add(tex)
class MathTeXDemo(Scene):
def construct(self):
rtarrow0 = MathTex(r"\left(\sqrt{a^2-b^2}+\frac{\sqrt{3}a}{2}{ ,\ -}\frac{b}{2}{ \ }\right){ \ }\cdot \left(\frac{\sqrt{3}a}{2}-\sqrt{a^2-b^2},{ \ }\frac{b}{2}\right){ =0\ }\Longrightarrow", font_size=44)
rtarrow1 = Tex(r"$\frac{3a^2}{4}-\left({a^2-b^2}\right){ -}\frac{b^2}{4}{ =0}$", font_size=44)
self.add(VGroup(rtarrow0, rtarrow1).arrange(DOWN))
self.play(
rtarrow0.animate.rotate(PI), Rotate(rtarrow1, angle=PI), run_time=2
)
self.wait()
class BraceAnnotation(Scene):
def construct(self):
dot = Dot([-2, -1, 0])
dot2 = Dot([2, 1, 0])
line = Line(dot.get_center(), dot2.get_center()).set_color(ORANGE)
b1 = Brace(line)
b1text = b1.get_text("Horizontal distance")
b2 = Brace(line, direction=line.copy().rotate(PI / 2).get_unit_vector())
b2text = b2.get_tex("x-x_1")
self.add(line, dot, dot2, b1, b2, b1text, b2text)
class MobjectExample(Scene):
def construct(self):
myShift=4
p1= [1-myShift,1-myShift,0] #point a
p2= [9-myShift,1-myShift,0] #point b
p3= [3-myShift,5-myShift,0] #point c
p4= [3.63-myShift,2.63-myShift,0] #point I
p5= [3.62-myShift,1.02-myShift,0] #ποιντ Ε
p6= [4.53-myShift,3.98-myShift,0] #ποιντ z
p7= [2.18-myShift,3.35-myShift,0] #ποιντ H
trigono = Line(p1,p2).append_points(Line(p2,p3).points).append_points(Line(p3,p1).points)
aSide=Line(p1,p2) #side AB
bSide=Line(p2,p3) #side BC
cSide=Line(p3,p1) #side CA
a_text = Text('A').next_to(p1, DOWN)
b_text = Text('B').next_to(p2, DOWN)
c_text = Text('C').next_to(p3, UP)
self.add(aSide,a_text)
#self.play(FadeIn(aSide))
self.play(Create(aSide))
self.wait(1)
self.add(bSide,b_text)
self.play(FadeIn(bSide))
self.wait(1)
self.add(cSide,c_text)
self.play(FadeIn(cSide))
self.wait(1)
ai=Line(p1,p4)
self.my_draw_line(ai)
opposite_cSide=Line(p1,p3)
angle_text=r"\alpha"
self.my_draw_halfAngles(ai, aSide,opposite_cSide, angle_text)
bi=Line(p2,p4)
self.my_draw_line(bi)
opposite_aSide=Line(p2,p1)
angle_text=r"\beta"
self.my_draw_halfAngles(bi, bSide,opposite_aSide,angle_text)
# line = Line(p4.get_center(), p4.get_center()).set_color(ORANGE)
i_text = Text('I').next_to(p4, UP)
self.add(i_text)
#self.play(FadeIn(cSide))
self.wait(1)
ci=Line(p3,p4)
self.my_draw_line(ci)
opposite_bSide=Line(p3,p2)
angle_text=r"\gamma"
self.my_draw_halfAngles(ci, cSide,opposite_bSide, angle_text)
plots = VGroup()
rightangles = [
RightAngle(Line(p1,p2), Line(p4,p5),length=0.3, quadrant=(-1,-1), color=RED),
RightAngle(Line(p2,p3), Line(p4,p6),length=0.3, quadrant=(-1,-1), color=RED),
RightAngle(Line(p3,p1), Line(p4,p7),length=0.3, quadrant=(-1,-1), color=RED),
]
for rightangle in rightangles:
plots.add(rightangle)#.set_fill(GREEN, opacity=1)
#p5= [3.62-myShift,1.02-myShift,0] #ποιντ Ε
r1=Line(p4,p5)
self.my_draw_line(r1)
e_text = Text('E',font_size=36,color=RED).next_to(p5, DOWN)
plots.add(e_text)
#self.wait(1)
#p6= [4.53-myShift,3.98-myShift,0] #ποιντ z
r2=Line(p4,p6)
self.my_draw_line(r2)
z_text = Text('Z',font_size=36,color=RED).next_to(p6, RIGHT)
plots.add(z_text)
#p7= [2.18-myShift,3.35-myShift,0] #ποιντ H
r3=Line(p4,p7)
self.my_draw_line(r3)
h_text = Text('H',font_size=36,color=RED).next_to(p7, LEFT)
plots.add(h_text)
r_text = Text('r',color=RED).next_to(r2, UP).shift(0.7*DOWN)
plots.add(r_text)
r_text = Text('r',color=RED).next_to(r3, DOWN).shift(0.4*UP)
plots.add(r_text)
r_text = Text('r',color=RED).next_to(r1, RIGHT)
plots.add(r_text)
self.play(Create(plots),run_time=3)
inCircle = Circle(1.63).shift(p4) #p4.y-p1.y=1.63 ok
self.add(inCircle)
self.play(Create(inCircle))
self.wait(1)
aei_triangle = Polygon(p1,p4,p5)
aei_triangle.set_fill(BLUE, opacity=0.5) # set the color and transparency
self.play(Create(aei_triangle))
aeh_triangle = Polygon(p1,p4,p7)
aeh_triangle.set_fill(BLUE, opacity=0.5) # set the color and transparency
self.play(Create(aeh_triangle))
q1= [0-myShift,6-myShift,0] #point Θ
q2= [2.62-myShift,6-myShift,0] #point ι
q3= [2.62-myShift,7.63-myShift,0] #point k
q4= [0-myShift,7.63-myShift,0] #point l
aei_transferred_triangle = Polygon(q1,q2,q3)
aeh_transferred_triangle = Polygon(q1,q3,q4)
self.play(Transform(aei_triangle, aei_transferred_triangle))
self.play(Transform(aeh_triangle, aeh_transferred_triangle))
x1_text = Text('x', font_size=36,color=BLUE).next_to(Line(p1,p5), DOWN)
x2_text = Text('x', font_size=36,color=BLUE).next_to(Line(p1,p7), LEFT).shift(0.6*RIGHT)
x3_text = Text('x', font_size=36,color=BLUE).next_to(Line(q1,q2), DOWN)
self.play(
Line(p1,p5).animate.rotate(PI),x1_text.animate.rotate(PI),
Line(p1,p7).animate.rotate(PI),x2_text.animate.rotate(PI),
Line(q1,q2).animate.rotate(PI),x3_text.animate.rotate(PI), run_time=4
)
self.wait(1)
bei_triangle = Polygon(p2,p4,p5)
bei_triangle.set_fill(YELLOW, opacity=0.5) # set the color and transparency
self.play(Create(bei_triangle))
bez_triangle = Polygon(p2,p4,p6)
bez_triangle.set_fill(YELLOW, opacity=0.5) # set the color and transparency
self.play(Create(bez_triangle))
s1= q2 #point ι
s2= q3 #point k
s3= [8-myShift,6-myShift,0] #point M
s4= [8-myShift,7.63-myShift,0] #point N
bei_transferred_triangle = Polygon(s1,s2,s3)
bez_transferred_triangle = Polygon(s2,s3,s4)
self.play(Transform(bei_triangle, bei_transferred_triangle))
self.play(Transform(bez_triangle, bez_transferred_triangle))
y1_text = Text('y', font_size=36,color=YELLOW).next_to(Line(p2,p5), DOWN)
y2_text = Text('y', font_size=36,color=YELLOW).next_to(Line(p2,p6), RIGHT).shift(2*LEFT)
y3_text = Text('y', font_size=36,color=YELLOW).next_to(Line(s1,s3), DOWN)
shapes = VGroup(y1_text ,Line(p2,p5),y2_text,Line(p2,p6),y3_text,Line(s1,s3))
self.play(ShowIncreasingSubsets(shapes),run_time=1.5)
self.wait(1)
##
chi_triangle = Polygon(p3,p4,p6)
chi_triangle.set_fill(GREEN, opacity=0.5) # set the color and transparency
self.play(Create(chi_triangle))
czi_triangle = Polygon(p3,p7,p4)
czi_triangle.set_fill(GREEN, opacity=0.5) # set the color and transparency
self.play(Create(czi_triangle))
t1= s3 #point M
t2= s4 #point N
t3= [9.62-myShift,6-myShift,0] #point ksi
t4= [9.62-myShift,7.63-myShift,0] #point o
chi_transferred_triangle = Polygon(t1,t2,t3)
czi_transferred_triangle = Polygon(t3,t2,t4)
self.play(Transform(chi_triangle, chi_transferred_triangle))
self.play(Transform(czi_triangle, czi_transferred_triangle))
z1_text = Text('z', font_size=36,color=GREEN).next_to(Line(p3,p6), RIGHT).shift(0.5*LEFT)
z2_text = Text('z', font_size=36,color=GREEN).next_to(Line(p3,p7), LEFT).shift(.5*RIGHT)
z3_text = Text('z', font_size=36,color=GREEN).next_to(Line(t1,t3), DOWN)
shapes = VGroup(z2_text ,z1_text,z3_text)
self.play(ShowIncreasingSubsets(shapes),run_time=1.5)
self.wait(1)
rr2_text = Text('r', font_size=36,color=RED).next_to(Line(q1,q4), LEFT)
shapes = VGroup(rr2_text ,Line(p4,p5),Line(q1,q4),r_text)
self.play(ShowIncreasingSubsets(shapes),run_time=1.5)
self.wait(1)
blue_rectangle = Polygon(q1,q4,t4,t3).set_fill(BLUE, opacity=0.5) # set the color and transparency
self.play(Create(blue_rectangle))
final_tex0 = MathTex(r"(BlueRectangle)=r\cdot(x+y+z)", color=GOLD, font_size=36).to_corner(RIGHT).shift(UP)
self.add(final_tex0)
self.wait(1.5)
self.play(Uncreate(blue_rectangle))
final_tex0_5= MathTex(r"(BlueRectangle)=(ABC)", color=GOLD, font_size=36).to_corner(RIGHT).shift(0.5*UP)
self.add(final_tex0_5)
self.wait(1)
self.play(Create(trigono.set_fill(BLUE, opacity=0.5)))
final_tex1 = MathTex(r"(ABC)=r \cdot (x+y+z)", color=GOLD, font_size=36).to_corner(RIGHT).shift(0.5*UP)
self.play(TransformMatchingTex(final_tex0_5, final_tex1))
self.wait(1.5)
self.play(Uncreate(trigono))
perimeter1 = MathTex("perimeter=","AB","+","BC","+","CA",color=GOLD, font_size=36).to_corner(LEFT).shift(UP+0.4*LEFT)
perimeter2 = MathTex("perimeter=","x+y","+","y+z","+","z+x",color=GOLD, font_size=36).to_corner(LEFT).shift(UP+0.4*LEFT)
perimeter3 = MathTex("perimeter=","2","*","(x+y+z)",color=GOLD, font_size=36).to_corner(LEFT).shift(UP+0.4*LEFT)
perimeter4 = MathTex("2s=","2","*","(x+y+z)",color=GOLD, font_size=36).to_corner(LEFT).shift(UP+0.4*LEFT)
perimeter5 = MathTex("s=","x+y+z",color=GOLD, font_size=36).to_corner(LEFT).shift(UP+0.4*LEFT)
self.add(perimeter1)
self.wait(1.5)
self.play(TransformMatchingTex(perimeter1, perimeter2))
self.wait(1.5)
self.play(TransformMatchingTex(perimeter2, perimeter3))
self.wait(1)
self.play(TransformMatchingTex(perimeter3, perimeter4))
self.wait(0.5)
self.play(TransformMatchingTex(perimeter4, perimeter5))
self.wait(0.5)
final_tex2 = MathTex(r"(ABC)=r \cdot s", color=GOLD, font_size=36).to_corner(RIGHT).shift(0.5*UP)
self.play(TransformMatchingTex(final_tex1, final_tex2))
self.wait(1.5)
framebox1 = SurroundingRectangle(final_tex2, buff = .1)
self.play(Create(framebox1),)
self.wait()
final_tex3 = Text("The Area of a triangle \nis equal to the product\nof its inradius (r) \nand semiperimeter (s)", color=GOLD, font_size=24).next_to((final_tex2),DOWN).shift(0.5*LEFT)
self.play(FadeIn(final_tex3))
self.wait(1)
framebox2 = SurroundingRectangle(final_tex3, buff = .1)
self.play(ReplacementTransform(framebox1,framebox2),)
self.wait(1)
def my_draw_line(self,r):
self.add(r)
self.play(Create(r))
self.wait(1)
def my_draw_halfAngles(self,ai, aSide,opposite_cSide,angle_text):
a_1 = Angle(aSide, ai, radius=0.5, other_angle=False)
tex1 = MathTex(angle_text).move_to(
Angle(
aSide, ai, radius=0.5 + 3 * SMALL_BUFF, other_angle=False
).point_from_proportion(0.5)
)
a_2 = Angle(ai, opposite_cSide, radius=0.5, other_angle=False)
tex2 = MathTex(angle_text).move_to(
Angle(
ai, opposite_cSide, radius=0.5 + 3 * SMALL_BUFF, other_angle=False
).point_from_proportion(0.5)
)
## self.add(a_1, tex1, a_2, tex2)
self.play(FadeIn(a_1))
self.play(FadeIn(tex1))
self.play(FadeIn(a_2))
self.play(FadeIn(tex2))
self.wait()
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