The Cosine Law

[JokotaJonas10]

Thanks so much!!! :) reviewing for my final and your videos are huge help!!

[308728823]

U DA BEST MAN XD

[monguiller]

who are those 2 dislikers XOO i hate you two!!! this tutorial is the best!!!!!!

[profuckenguy]

man i think my teachers been teaching me the wrong shit for a week

[StupidKidsFiles]

how do u get an angle when you know ALL of the sides but no angles??

[AlRichards314]

@StupidKidsFiles When you are given three sides, but no angles you use the formula solved for Cos of an angle. See the first page on the video, the three formulas in red on that page. There is an example on the second page of the lesson showing how to find an angle given 3 sides.

[theonlyreega]

what if you have 2 angles and 1 side given?

[AlRichards314]

@theonlyreega If you have 2 angles given and a side, then you really have all 3 angles (sum to 180) and a side. This isn't the senario where you can use the Cosine Law since you need 2 sides to find the third one using Cos Law. However, when you have 3 angles and a side you can use the Sine Law to find the other 2 sides. Actually, you could use the Sine law to find a second side and then once you have 2 sides and 3 angles you could use either the Cos or Sine Laws to find the remaining side.

[msyangmath]

Great clear video. Forgive me if I missed this somewhere in the video but did you go over the disclaimer: If given SSS then find largest angle first, and if given SAS, find the third side, then the smaller angle first?

If not, then problems occur where the math is correct but the solution simply is not. Example for SSS, a=5, b=7, c=10. If you solve for A first, it leads to a wrong angle. For SAS, A = 50 degrees, b=12,c=5. If you solve for B first, then it would lead to a wrong angle.

[ArdinTheCreaToR]

you are are the fucking man, saved my ass with this shit, OFWGKTA

[jhneureko123]

Oh thankyouuu very much => You people are so awesome. I understand things at once especially the derived formulas. Teachers tend to discuss lessons like this for 2 days, and people still don't get it.

[BigPappiO]

@BigPappiO No i fail.

[xXSnapCrackLeXx]

Thanks so much for this video, my teacher spent 3 days teaching us this and you helped me understand it better in just 10 minutes..

[RandomAccount922]

Wtf man 10 min of studying this video I get a 100% but 4 hours of class time and I get a %50 thank for the vid stupid teachers

[YeahAndThat]

2weeks of class... Don't get it. 10 mins on YouTube ... Oh thatsss easy

[SobiLove24]

awesome job!

[NathanSkatesBTL]

I feel like I will actually pass my math exam now! thanks a lot

[00Mj000]

u know what, McDonald's here i come

[DJJayday]

2 people must have been retarded...

[SKarletKennedy]

This is very easy to understand I don't know why there are 2 dislikes?

Thanks

[zaqqy2010]

not sure how u got that 55 as the answer for cosC

[AlRichards314]

@zaqqy2010 In the second example cosC = 0.5676, so C = cos^-1(0.5676) = 55 degrees. The cos^-1 function on a scientific calculator gives the angle when you know the cosine decimal value. Make sure your calculator is in degree mode and not radians or gradients.

[ngrbugu]

thanks,very clear presentation

[loveux29]

thanks!

[kqncept]

Thanks a lot, very clear and descriptive. Easy to understand as well, I'll pass my test today no doubt ^_^

[WashiNBPro]

u are far way better than my teacher, very clear and understandable...

if they had more online lessons like this,

it would have been better for me and i guess for others too ..

[AlRichards314]

@WashiNBPro Hey, thanks for the comment. I appreciate hearing from people that find my videos useful (this is exactly why I shared them on YouTube). Thanks again, Al

[OVER9000VIDEOS]

This is grade 10 math..

[AlRichards314]

@OVER9000VIDEOS This is the grade 11 version of my Cosine Law lesson. If you want the grade 10 version look for Cosine Law (Grade 10).

[OVER9000VIDEOS]

@AlRichards314 I just completed my grade 10 math test using this lesson. The one you call grade 10 is not relevant to what I'm learning.

[AlRichards314]

@OVER9000VIDEOS The grade 10 lesson is based on the curriculum for the province of Ontario, Canada. If you are studying soemthing else, then it will not necessarily matchup. If you do live in Ontario Canada, and your teacher gives you material not in the grade 10 curriclum, then it will not correspond either.

[LikeItDeep]

very clear. thanks

[uriel17051993]

tanks soo mcuh :DD i love youtube :P

[ultrawaseem]

my teacher is a fucking crack head no joke he told us his story and he doesnt even know how to teach and when he doesnt feel like teaching he ells us to go on you tube thats fucked

[uriel17051993]

@ultrawaseem report him lol :P

[AloysBarron]

thank you so much for this! seriously!

[zingy101]

thanks alot :)

[0501701]

do all your solutions qualify for ontario curriculum communication marks?

[AlRichards314]

@0501701 Anything can be marked with respect to communication. You can look for proper units and mathematical symbols, clearness of arguments or reasoning and also communication for different audiences. One or more of these could be found in virtually any solution.

[ludacrizzmoney2]

For example 2 if you were to use the Sine Law for Angle B u would get an answer of 87.75..., and if u were to round that it equal 88, and then if u were to use Sum of interior angles in a triangle angle C= 56. Why is that? Am i doing in a wrong order? or are u doing it wrong?

[ShortStaturedPickle]

Thank you so much for posting this! I understand what I was doing wrong now!

[allennorei]

thank you!!!

[shill61]

Finally, finally i get it i took you 10 minutes to show me what that dumb bitch has been talking about for days

[RayL93]

OMG Thank You! You've just taught me faster and better then my Grade 10 teacher!

[HockeyLyfe1]

Ok thank yu, This lesson helped me pass my Math Exam :)

[HockeyLyfe1]

Wht Garde math is this

?

[AlRichards314]

This lesson was for a grade 11 math class in Ontario, Canada.

[Nima5124]

Thank You! I really understand it now!

[TomaaatoZo]

Thanks again!