30-60-90 triangle side ratios proof | Right triangles and trigonometry | Geometry | Khan Academy

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  • เผยแพร่เมื่อ 22 ธ.ค. 2024

ความคิดเห็น • 55

  • @sdhafele5003
    @sdhafele5003 6 ปีที่แล้ว +8

    If you draw an isoscolese triangle with the 2 congruent sides labled as "a," the triangle's height, h, will split the base, b, into 2 parts. If one of those parts is x, the other MUST be b-x. By the Pythagorean Theorem, x^2+h^2=a^2. By the Pythagorean Theorem, (b-x)^2+h^2=a^2. Using the Algebraic Identity (a-b)^2, you'll now know that b^2-2bx+x^2+h^2=a^2. Replacing x^2+h^2 w/ a^2 gives you b^2-2bx+a^2=a^2. Solving this equation for x tells you that x, one of the base's 2 parts, is b/2. The other part of the base, b-x, is b-(b/2), or, (2b/2)-(b/2), or simply b/2. All this proves that the height of an isoscolese triangle cuts the base of the triangle in half.

  • @MikeCasey311
    @MikeCasey311 ปีที่แล้ว +4

    Thank you, thank you. Every other video used these values without proof. 👍👍🇺🇸

  • @standardservices7573
    @standardservices7573 4 ปีที่แล้ว +4

    this really helped in my exams thanks

  • @MoonLight11023
    @MoonLight11023 11 ปีที่แล้ว +3

    therefore, the length of the sectors AB, BC, and AC are equal. It's concluded that AB line = BC line = AC line. BD line = CD line = 0.5*AB line = 0.5*AC line.
    I hope it helps :)

  • @MoonLight11023
    @MoonLight11023 11 ปีที่แล้ว +3

    This theorem can be proven by inscribing a 60-60-60 triangle (ABC) in a circle. Draw AB line such that it makes an angle of 30 deg with the horizontal diameter of a circle, drawn in a Cartesian coordinate system, of a center point (0,0). Then, draw BC line such that it makes right angle with the horizontal diameter and then draw AC line. Since BC line is perpendicular to the horizontal diameter, therefore, BC line is bisected by the horizontal diameter in, let's say, D point. Continued.....

  • @MoonLight11023
    @MoonLight11023 11 ปีที่แล้ว +2

    If we look closely we will find out that two congruent right triangles are formed ADB and ADC. As a conclusion, BD line = DC line = 0.5*BD line. ABD angle = ACD angle = 60 deg. DAB angle = DAC angle = 30 deg. It's concluded that ABC is a 60-60-60 triangle. The inscribed angles, BAC, ABC, and BCA are equal to 60 deg and they are equal to half of their central angles each. Sector length = radius* angle(rad). Since the three angles of the inscribed 60-60-60 triangle are equal, therefore,Continued..

  • @lukababilodze4283
    @lukababilodze4283 6 ปีที่แล้ว +10

    Thank you my math teacher doesn’t know how to teach us properly. (Of course she has the knowledge tho)

    • @EDward-u1f6i
      @EDward-u1f6i 4 ปีที่แล้ว +1

      I doubt she has the knowledge xD

    • @lukababilodze4283
      @lukababilodze4283 4 ปีที่แล้ว +3

      @@EDward-u1f6i lol I just saw a reply on my comment. I don't even remember commenting this. At least now I know that she does not have the knowledge XD I was in probably like 9th grade at the time

    • @zurabkhutsishvili8754
      @zurabkhutsishvili8754 2 ปีที่แล้ว

      @@lukababilodze4283 :DDDDDDDDD mecxre klasshi tu ameebs uyurebdi sagol shen dzmao

  • @trentonbouchard988
    @trentonbouchard988 6 ปีที่แล้ว +4

    Perfect. I needed this video. I finally get it

  • @natcat1324
    @natcat1324 12 ปีที่แล้ว +4

    It is easier to think about to have the short leg as x, the long leg as x√3, and the hypotenuse as 2x.

    • @jordieb3333
      @jordieb3333 3 ปีที่แล้ว

      Please explain madam, i have a test in IM3 and i dont understand this man he did the pythagorean theorem incorrectly and wrote a random 4 at the end and my mind is having difficulties

  • @lenoraelaine
    @lenoraelaine 8 หลายเดือนก่อน

    That was fun!

  • @ThomasGiles
    @ThomasGiles 11 ปีที่แล้ว +6

    I think I get it now. Took a a lot of re-watching. Towards the end, you were moving a bit fast, I think.

  • @Ensign_Cthulhu
    @Ensign_Cthulhu 13 ปีที่แล้ว +1

    @Veronicaboost You can never watch too much Khanacademy before a test. Provided of course that it's relevant to the test...

  • @katrinaultriyama7143
    @katrinaultriyama7143 6 ปีที่แล้ว +1

    can you help me with this problem?
    "The Pythagorean theorem is used to prove the side lengths of a right triangle. Use complete sentences to describe the proof of a right triangle with sides lengths of 7 meters, 24 meters, and 25 meters."

    • @palereaper
      @palereaper 4 ปีที่แล้ว

      no idea man

    • @jordieb3333
      @jordieb3333 3 ปีที่แล้ว

      im 3 yrs too late, but its saying use the pythagorean theorem to prove why that right triangle has side lengths of 7m, 24, and 25m and detail in a explanation . so just give an example, for example lets say 25 was x, you would write down your use of the pythagorean theorem(A^2+B^2=C^2) to get 25 its actualy pretty simple if you dissect the question a bit. I know it wont help but maybe this will help another kid looking for answers.

  • @skateraptor12
    @skateraptor12 5 ปีที่แล้ว

    How is the leg bigger than the hypotenuse then when the hypotenuse is 10 radical 3? That means that 10 radical 3 times radical 3 all divided by 2 is 15?

  • @dildobaggins2759
    @dildobaggins2759 4 ปีที่แล้ว +2

    "Khan academy ime gonna drop an altitude". Me: "Just say you drew a line"...

    • @elmosarmata9561
      @elmosarmata9561 3 ปีที่แล้ว +1

      It's the correct mathematical term tho.

    • @dildobaggins2759
      @dildobaggins2759 3 ปีที่แล้ว +3

      @@elmosarmata9561 Yeh but more people will understand draw a line you want to make maths as simple as possible to people when you teach. Or anything in general no need to use complex terms for no reason.

    • @thecosmos7671
      @thecosmos7671 2 ปีที่แล้ว

      Altitude is more appropriate because a line could project any angle at the opposite side but an Altitude projects a 90° angle and that makes it easy for us to use Pythagorean theorem and also in an equilateral triangle a median is an altitude. A median is a line drawn from the vertex to the opposite side which bisects (divides in 2 equal parts) the opposite side
      Hope this helps

  • @suadali1017
    @suadali1017 9 ปีที่แล้ว +1

    Thank you so much .

  • @shridhar1286
    @shridhar1286 12 ปีที่แล้ว

    your genius

  • @ThomasGiles
    @ThomasGiles 11 ปีที่แล้ว +2

    Why are we multiplying and voiding by 4

  • @aneeshsunny7274
    @aneeshsunny7274 8 ปีที่แล้ว

    Well nice cud xplain in a better way

  • @novanova4737
    @novanova4737 8 ปีที่แล้ว

    just draw an right angled triangle then construct another right angled triangle then prove the whole triangle to be equiangular triangle then start the proof it is the easiest method

    • @afkoppauthor
      @afkoppauthor 6 ปีที่แล้ว

      Some people can't get it as fast as others though. Everyone has a different way of thinking.

  • @faridhussainmirza4524
    @faridhussainmirza4524 8 ปีที่แล้ว

    nice video

  • @jonathan8114
    @jonathan8114 3 ปีที่แล้ว +2

    Where on earth did he get all those 4s, he just kept on adding them out of nowhere, someone please explain?

    • @jordieb3333
      @jordieb3333 3 ปีที่แล้ว +2

      fr lol but he got x^2/4 from simplifying (x/2)^2 but the 4x^2/4 i have no idea

    • @Jamey-xm1dd
      @Jamey-xm1dd ปีที่แล้ว +2

      He just made X^2 into 4x^2/4 to get a common denominator, making it easier to subtract x^2/4 from 4x^2/4 which equals 3x^2/4.

  • @LordOfNoobstown
    @LordOfNoobstown 4 ปีที่แล้ว

    why can't you take the square root first in your final proof on x sqrt(3)/2

  • @GabrielOrtiz-dv4jk
    @GabrielOrtiz-dv4jk 8 ปีที่แล้ว

    What about the square 3??

  • @ninderchitosiya5326
    @ninderchitosiya5326 8 ปีที่แล้ว

    Sr hindi me post krna plz
    ya hindi medium ka koy channel btana plz

  • @bofa-zi4fj
    @bofa-zi4fj 7 ปีที่แล้ว +2

    why is (BD)^2 not simplified to B^2 D^2?

  • @lifer7741
    @lifer7741 2 ปีที่แล้ว +1

    Someone explain how that 4x²/4 turned into 3x²/4

    • @thecosmos7671
      @thecosmos7671 2 ปีที่แล้ว

      It didn't turn into √3 s^2/4
      Acc to Pythagoras Theorem we have a^+b^2=c^2
      Here,we know C and b so to get a we write
      C^2-b^2=a^2
      C=X, b=X/2
      So , x^2-(X/2)^2=3x^2/4
      On taking square root we get
      √3x/2.
      I hope it helped

    • @lifer7741
      @lifer7741 2 ปีที่แล้ว +1

      @@thecosmos7671 yes i understand, thank you.
      But wait how did x²-(x/2)² equal to 3x²/4?

    • @thecosmos7671
      @thecosmos7671 2 ปีที่แล้ว

      @@lifer7741
      Okay let me explain.
      You can write x^2-(x/2)^2 as
      x^2-(x^2/4) okay.
      Now, we'll make their denominators equal so that we can do subtraction
      So we'll make x^2 =4x^2/4 (multiplying and dividing by the same number preserves the equality,means it does not change the original value ,its just easier for us to compute, otherwise we'd have to take LCM. well it's the same as taking LCM but I guess it comes more easily)
      So , 4x^2/4-x^2/4 =3x^2/4 ( if it's not clear here then suppose x^2/4 is a mango
      So 4 mangoes-1 mango =3 mangoes ( now put the value we assumed to be a mango in the result.)
      Which means 3 *x^2/4
      I hope I helped ⭐

  • @babyhppoo5763
    @babyhppoo5763 6 ปีที่แล้ว

    What's that weird thing they have thats Like the square root of three and stuff

  • @shahdrashed5938
    @shahdrashed5938 7 ปีที่แล้ว

    Math proplems in exam paper: Solve me!?
    Me. Lol.

  • @brooklynnmiller8446
    @brooklynnmiller8446 8 ปีที่แล้ว +2

    HOW THE FUCK DID YOU GET A FOUR!!!!

    • @josiahm5221
      @josiahm5221 8 ปีที่แล้ว

      He simplified (x/2)^2. 2^2=4 and x^2=x^2 making x^2/4

  • @julescallanta6539
    @julescallanta6539 5 ปีที่แล้ว

    My teachee told m that the opposite of the 30° was always x and the opposite of 60° is x/3 and the other is 2x

  • @tuckersawyer4414
    @tuckersawyer4414 7 ปีที่แล้ว

    why do you have x/2 in this video for the short sides but in reality its x. why?

    • @afkoppauthor
      @afkoppauthor 6 ปีที่แล้ว

      It depends on who teaches it. It all depends on if the hypotenuse is 2x (when the short side is x), or if the hypotenuse is x (when the short side is x/2). it all depends on the teacher. :)

  • @NarcoticNKO45
    @NarcoticNKO45 13 ปีที่แล้ว

    @dere60 ikr

  • @cinnamonbeanz2620
    @cinnamonbeanz2620 6 ปีที่แล้ว

    This still makes no sence to me.

    • @kabascoolr
      @kabascoolr 6 ปีที่แล้ว

      Watch his earlier video on isosceles triangles, and the one on Pythagorean theorem. Most of the ideas for this video comes from those.

  • @novanova4737
    @novanova4737 8 ปีที่แล้ว +3

    meaningless video just made difficult for students