Foci of a hyperbola | Conic sections | Algebra II | Khan Academy

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Introduction to the foci (focuses) of a hyperbola
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[@neilsklar3509]

Sal is a truly gifted teacher, but this isn't one of his better lessons. The frequency with which he starts and then abandons sentences mid-stream here makes for a very fragmented learning experience.

[@jandy608]

For me, when I'm using the formula for an ellipse, I tend to not use the variables a and b as "horizontal" or "vertical" radii. I would rather just say that the variable a represents the major radius instead of whatever the horizontal radius is. Same for b, I tend to use that as the shorter radius (minor). I think this is just an easier way or referring to these radii when I'm using the formula for an ellipse to find the foci/focal distance

[@nycscuba11]

To determine which way they Hyperbola opens can be simplified by saying whenx^2 is proceeded by a plus sign it is horizontal or When y^2 is proceeded by a plus sign the transverse axis is vertical. Or even simpler which ever is written first being the plus one is always written first in standard form. Very helpful video

[@Chordinated]

i was tought that no matter what a>b. a is always the semi major axis and b is always the semi minor axis. i'm sure either works but i find it interested that both ways are tought, i'm sure this has lead to some confusion

[@inuyome1008]

I do love his voice.

[@payasitopimpim2002]

thanks for all... khanacademy .....your useful lessons .....from lima peru

[@e1ghtSpace]

13:46 Oh thank god, I was like "Aww man, I have everything backwards."

[@jonnachi]

If we are graphing and we got the foci from the a^2-b^2=c^2.. Do I count from the vertex of the hyperbola or from the center to graph?

[@silencedidgood]

How can you produce videos longer than 10 minutes for You Tube? I'm lovin having one spot to both look at the math of kinematics and the Paulson plan!

[@kiwilimepi1]

How would you find the vertices?

[@nononnomonohjghdgdshrsrhsjgd]

if you put y to zero, you will get the smallest absolute (positive and negative) value of x, which is the vertex by 0 shifting. It is the smallest value, because of the minus sign between x squared and y squared in the equation. if you put instead y to zero, you will get for hyperbola around the x axis complex rooots resp. there are no real roots, therefore there is no intersection with y axis of real numbers.

[@farhannajme7542]

Thank you so much

[@DanielRamirez-uc4kl]

The whole video: was useless to me until 12:40

[@phancakes6219]

Right? At least 12 minutes wasted....

[@readthesecomments]

i think you should make videos about how to be as cool as you

[@aeropostale4277]

how do you know which one is a or b? is it always under one axis?

[@onlyme0101]

a to x and b to y axis

[@ThatsJustLardy]

dang. thought it was folk-eye

[@wedeldylan]

You can say it either way kzbin.info/www/bejne/rX3Nfn94g9CDhJI

[@noncanadian]

@454ffv it appears you need to polish up those math skills of yours kind sir (it could be y=[4/2.5]x though)

[@InternetSandman]

the alarm going off in the background really kept making me take my headphones off cause I thought it was from my own room lol

[@454ffv]

at 14:00 wouldnt the line be y=4/3x?

[@khoembunnamath2738]

can you explain me about directrix of hyperbola.

[@ssn90]

Does hyperbola even have a directrix??

[@sanyamjain7058]

@@ssn90 yes ofcourse

[@CH1EFBL1TZ]

at 13:05 he messed up. Hyperbola is minus not plus between the x squared and y squared

[@belogical2396]

Li Jimmy your repied on a 8 yo comment

[@noncanadian]

i dont even remember this conversation its been so long, don't dig up old comments and annoy people please...

[@ReganQuinn]

i am still struggling wiht finding the solution to a Hyperbola in standard form... and finding the foci and verticies!

[@aeropostale4277]

this is confusing ):

[@shanesantos5396]

They're teaching us these things (and more) in tenth grade. I feel like it's too advanced. Gosh, math, why you do dis to me?!

[@hhaze2020]

WTH we are never even taught conic section in Alevel,just gotta learn this shiote for college entry tests

[@brennano1487]

where the fuck is the volume?

[@noncanadian]

@454ffv meant to say y=[4/2.25]x... doesn't change the fact that you're still wrong... (you said) 4/3 =1.3 | (i said) 4/2.25 =1.7(repeating) | (he said) 16/9 =1.7(repeating)... Get It? Good! Get Out House!

[@je.dansky]

...fair enough.

[@cardboardpox]

is anyone else cramming for tomorrow's finals?

[@evelyngamez6819]

it looks like gibberish

[@nikkikali9507]

I thought this was going to help me learn to find the foci in a hyperbola. But it doesn't! If your going to make a video about hyperbolas, then don't talk about ellipses.

[@TsukikoKutamora]

Nikki Kali I was looking for the same thing

[@nikkikali9507]

Tsukiko Kutamora were you able to find the foci from this video?

[@TsukikoKutamora]

Nikki Kali I didn't

[@HEMANTYADAV-xp6pt]

Bad

[@NotLegato]

you are really struggling with your wording here. when making educational videos for the whole world, you oughta at least practice the ones you struggle with.