Trigonometry: Finding an Equation from a Graph

[BlenderFreak777]

Wow, I wish you were my teacher...all my teacher does is examples, with his back towards us, as if hes was doing the problem. He doesn't explain why the graph looks the way it does, he just expects us to decipher our notes.

[cschuck320]

thank you for mis-saying a few things wrong. it makes you more of a teacher to me (and I'm assuming others) when it doesn't feel like a written transcript

[aRITZNproduction]

my math teacher tried to teach me this she sucks but this guy is nice

[MakeleleToulalan]

very helpful thank you

[WarlordRiley]

thank you very much

[EyyyitsKAYYBEE]

VERY helpful =)

[qq123456ww]

nice

[0810polly]

how do you know that it is reflected?..i cant tell the difference.:(

[cschuck320]

@0810polly its y-intercept is a negative, rather than a positive?

[KCAASE]

In case any of you needs to know. The gentleman in the video is Dr. Charles P. McKeague himself. He is a math professor and the author of college level math textbooks.

[Emregames]

That was amazing

[AwesomeViralVideos]

weve been seeing each other for a long time now... would you be my math teacher?

[DahStoryTella]

How do you know that the amplitude is 3?

[loler4eva]

@DahStoryTella amplitude in max-min / 2

[iAmEvanX]

where do you get the "B co-efficient" from? the 2pi/3? help please :(

[PlasmaPrestige]

@iAmEvanX

The formula is 2pi/B equals the period. You know the period, so therefore 2pi/period is equal to the absolute value of B (the coefficient). A conceptual way of understanding this is what number multiplied by 2pi/3 equals the parent function's period of 2pi. In math symbols, B(2pi/3)=2pi.

[xteaopia]

let down.

[HeAtBBx]

My mark was going slowly downward from F to U until i started watching these. Thanks so much.

[foreveryoung203]

This guy made my F turn to an A in one week. I <3 him.... :)

[Ceretia]

@1:20 Since the crest goes six points higher than the starting point, shouldn't the amplitude be 6 instead?

[iDonof]

@Ceretia you always count up from the x axis, don't count from the bottom of the graph

[PlasmaPrestige]

@Ceretia

A very important concept to remember is that amplitude is the distance from the BASELINE to the maxima/minima, NOT the minima to the maxima.

[mynameiskidd]

you are awesome

[saxyviolist]

I have been having SO much trouble in Trig this year. I don't understand why! I study hard, and I work hard...but it just doesn't work, as my average stays in the 75-ish area. It's sad for me, because I've always been great in math. I wish I discovered your videos before! But this is pretty helpful, and I hope I WON'T fail my test tomorrow....I'm kind of scared for it. But thanks for posting such great videos!

[tdlob1]

Thank you thank you thank you!

2 minutes in and I already understand!

[UryuOrihimelover4eva]

This is so helpful! I have a test with these kinds of problems, so this helps a lot! Thank you so much. :]

[probassangler31]

thumbs up for neat writing!

[reasatselim]

you are AWESOME!!!!!!!!!!!

[ak137lg]

why are all youtube teachers better than the ones at school

[r1oot]

You're teaching is really organized and direct to the point. Thank you!! 

[blancoisgod]

wow.

You sir made complex math so much simpler. Wheres the donate button?

[AZNelite666]

my math teacher fucking sucks, this is freaking amazing

[EaglesGiveYouWings]

You ROCK! For some reason I couldn't understand the concept of getting an equation out of a graph. You helped me out big time.

[M55ikael]

How can you you see right away that it's cosine graph as opposed a sine?

[st335533]

@M55ikael a silly way i learned which i got from patrickjmt (another math tutor video is SIN STARTS at ZERO (if u say it it sounds funny lol) so just remeber sin starts at zero, if it starts on the amplitude its cosine, if it looks like a curvy stick thats just standing outa nowhere its tangent =D

[st335533]

@st335533 omg im teaching math to someone ?!?! GREAT SCOTT! WERE ON TO SOMETHING!!!

[blancoisgod]

@M55ikael

cosine graph looks like a U

a sine graph looks like a squiggly line ~

[TormiTormi]

great explaination!

[nivadalinux]

but my teacher says that he want to see my solution, of how i get the amplitude and Perimeter not just by looking on the problem ^_^ i don't understand what he says about the solution, since i got already the Amplitude and the perimeter...

[OmarChannel]

This guy does easy questions do harder ones, so we can actually learn.

[ger6master]

do you make the voice for Microsoft Sam?

[utonium]

THANK YOU VERY MUCH FOR THIS VID!! You made it very clear to understand!!

[Dealingmafia]

I use to find this hard to get periods of the graph but now it's a breeze after watching this tutorial.

[deathsmage]

He completely missed the one thing i was watching this video for, phase shifts. Other than that, this video was helpful.

[Gutsyndicate]

thank you very much, I understand it all, my teacher make it harder.

[AutopsyReport22]

why didn't u give an example of one w/a phase shift?????

[MwahAi]

Thanks for making this video! I have a test tomorrow about cosine/sine graphs and I somewhat get it now.

[MiturBinlsderty]

i wish this guy was my teacher!

[qiselle]

omgggggggggg you saved my life ive been studying for my pre calc quiz foreverrrrr and now i get it... thanks :)

[jen4123]

how'd he find b ??

[GuildmistressDeby]

@jen4123 . If you are referring to the "b" in the period formula then he just got it by cross multiplying. step 1. 2pi/B=2pi/3 step 2. 6pi =2piB then you divide both sides by 2pi to solve for B and you get 3 as your period

[fredcorp66]

its where the line crosses the vertical y axis

[ujaycoolio]

wow u were born to teach !

[jesusclau1]

Love your videos. You explain things very clearly. Thanx a bunch!!!!!

[MIS0HAPPI]

wow you make math so much easier

[loverofbeats]

these are easy, post complex ones.

[Ade161]

I WISH HE WAS MY TRIG TEACHER.

[theodore944]

what is (B)?!!!!!!!

[hectorltd]

b is ur y intercept

[hectorltd]

B in the trig function is ur frequency

[holman927]

I'm going to flunk.

[salmannooman92]

.......i dont get it

[TigressofDDR]

No phase shifts? Booooo.

[cosmogang]

Shunnnnnnnn.......

[Dat1Nerd]

OMG, I am up at 1:00 trying to this project, thank you soooo much for posting this, you're going to get me a good grade and let me get some sleep. Thnx again!

[MrCgcg333]

Thank you so much!! Thank you for taking the time to do this. I always take notes but seeing how to do it again greatly helps!!!

[starwarsfreakdood]

no phase shift?

[fancymoon2]

I wish you were my data management teacher. You are gifted in teaching.

[Mu5clehead]

@fancymoon2 this is grade 10 stuff, lol

[Vikki1331]

@Mu5clehead No it isn't A few of the graphs are, but the trigonometric function graphs are grade 12 and early college

[Mu5clehead]

@Vikki1331 I meant Grade 10 Math Enriched for gifted students.

[jrendoso]

thanks for caring and taking the time to teach in such a simple and clear way.

[sealoforicalchoas]

would this be in the gsce course?

[2pacoverbig]

nah- cuz they stoped gcse maths course work

[SkidRamrock]

what is the period? that would explain why he used 2 instead of 0.5.

[t0myuri]

period = wavelength

[mrcelada]

y=Pi*x+e

[KEKInc]

Oh, and also, the equation for the amplitude (A) is |(max-min)/2|. You probably would have figured it out anyways; it's relatively basic. The 'eyeballing' method of finding the amplitude in this video only really works when the principle axis is 0, which all of the examples were.

[xioda07]

it would be great if he did some phase shifted with it.

[KEKInc]

Yeah, just add C and D into the trig equation to do phase shifts.

f(x)=A sin(B(x-C))+D

(Sine can be replaced with cosine)

D is the principle axis (line between max and min; vertical shift).

D is |(max+min)/2| (note the absolute value bars). For the min and max, you would use the y-values.

C is the horizontal phase shift.

C is |(max of x + min of x)/2|. Just look for any local minimum and maximum and find the correlating x-value and plug it into this equation.

[Manifests]

Wow, this helped so much! Very clear instructions. Thanks MathTV!

[perriclez]

: i was really having a hard time understanding in class, you really clarified this concept using specific words, thanks.

[17Slaves]

Do you have any good rules for keeping track of your order of operations. Whenever I do these equations on my own I do it all backwards and upside down...

[payasitopimpim2002]

thanks a lot friend..from lima peru....

[denverspurple104]

you rock proffesor!

seriously though i have an exam/quiz in the morning tommarrow and i randomely searched trig help and THIS IS EXACTLY what will be on my test so thank you soo much!

[Knockturnall1]

hi everyone

[Knockturnall1]

yeah, thinking to much about a math problem will definately make you lose your hair...

[jonathaninter86]

am i gonna end up with that hair if i do too much math???

[knyazhnaalina]

This was very nice how he explained it, God has blessed him. But I think he didn't explain why the cosine curve was reflected (I know, because it was negative, but maybe other people don't know that) so just some little comment for future reference. :D God bless you to teach and bless other people!

[gunggong060969]

i see that he's a very good instructor of trigo...thanks a lot ...i understand it very clear...

[endonetto]

Thank you very much.

[vampgaze02]

yeesh at least do one with a phase shift and/or vertical displacement

[supercatracho]

thank you..!!!

[niharjhatn]

maybe a phase shift question would have been more helpful

[2high2aim]

thanks a lot do you teach? or tutor personally i checked out the site but are you a teacher???

[00MrPanda00]

This Was Very Helpful Thank You So Much ^_^