The Law of Cosines
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- čas přidán 4. 02. 2018
- The law of sines helped us solve for all the sides and angles in SAA, ASA, and SSA triangles, but now we have to learn the law of cosines if we want to solve for SAS and SSS triangles. This one is kind of like the pythagorean theorem, just for oblique triangles instead of right triangles, so it has trig functions in it. Let's check it out!
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![Law of Cosines - Formula, Examples & Proof - [2-20-4]](http://i.ytimg.com/vi/ac25DrPYSoc/mqdefault.jpg)
tysm! i fell asleep in class and this was our lesson for today. super helpful.
Maybe sleep outside of class?
@@Jbnfmshhwbbe1 wow cool idea, definitely worth trying, I generally sleep in class and study outside
I'm currently failing a test on this
bro i got a test tmrw on this.. and i'm just learning now
I have a test on this, buts it's in the next 2 hours
I hope you got better
Same LMAO
Im having an exam where Ill probably have to explain how to get thos😀
Great explanation
I love the intro
Same
Same hahaha
You prolly dont give a shit but does anybody know of a way to log back into an instagram account..?
I was stupid forgot my login password. I would appreciate any help you can offer me!
@Kristopher Alexis instablaster =)
@@kristopheralexis9911 press forgot password and enter email and check your email app and make sure to *refresh it* and then verify, then you can follow the instructions
Thank you, Professor. Dave!
Got subscribed! Great explanation.
oh my god you literally saved me thank u sm!!!
i like your smart way of teaching professor dave
so if I get it right when the answer is a negative you turn it to positive like in the example where cosC =-0.157 you did cos^-1(-0157) then got a positive 99.0 and that was the final answer. am I right ?
Thank you sir
you helped me so much!!!
thank you!
Thanks a lot
may I know how you got cos C = -0.157
In the comprehension i got 77.673 as cosA while you got 75. I used the cos rule and used the sides to calculate A. How did you do it to get 75? Thanks in advance.
Long advance
I got the same answer. All of my answers were different than his. I have no idea why.
Maybe your calculators were in radian mode? Or degree mode?
My answers were also not the same at first. My answers were 1 point something degree shorter than his but when I try using 4 decimal places, its now similar to professor dave's like in c = 13, I used 13.4164. However, when it is for the final answers, I rounded it off to get a whole number like B = 37.6328 -> 38
nice video and good graphics
how do you edit these videos 👍👌
adobe premiere and after effects!
Professor Dave Explains : awesome and thank you
I see you've only used 2 of the formulas so how to solve with b^2=a^2+c^2-2ac cos B?
Same method
you repeat the same steps just with different value
At 2:49 you say "just divide". Where does division come from? Thanks. very helpful.
When we move 2ab to the other side, it goes from multiplication to division.
This is transposing method .
thanq
done with trig after 2 weeks, yey
how did you get a= 7.92
this is because the equation has a^2 in it. So when you find the answer which was 62.7, you have to square root it because in the original equation it was A^2 = b^2 +c^2-2bc (cosA). So A^2 = 62.7, and A = sqrt 62.7 or around 7.92
How To Add, Sub , Divide And Multiple Degree With Out Calculator
Why did you just show how to do cosine law and didn’t show how to do sine law in the first question can’t really get anywhere if I can’t figure out to to do the sine law in that specific question
Plss.. upload videos of physics...
Yeah
dudes i did two entire physics series, classical physics and modern physics!
Professor Dave Explains he means do videos on Electrical or mechanical engineering courses!
You bear a slight resemblance to 66Samus, the death metal drummer. Emphasis on slight.
I'm from India....but I study from this video 🤩🤩
thank you papi
Sometimes I don’t know the difference between sine and tangent
go back to the earlier trigonometry tutorials for review!
Professor Dave Explains what was your field of study in university? What course did you study last time? What type of student are you?
i studied chemistry in undergrad, now i'm wrapping up a masters in science education
Professor Dave Explains what types of science? Is it on biotechnology, water & environment? If so make a video on wastewater treatment plants, or nitrogen cycle
Ur explanation is excellent. When u speak the words are also printed below in a box which obstructs the view of the formula. Perhaps u should use a different method of not having the screened box.
Plz upload a video about sine and cosine of obtuse angles
watch my whole trigonometry playlist it's all in there
@@ProfessorDaveExplains sadly can't find:-(
home page, scroll down to mathematics section, scroll right for trigonometry
@@ProfessorDaveExplains prof could u kindly just tell me the vid name or any hint I'll be grateful
czcams.com/video/cqIZue-plBI/video.html
You can go from here, a hint maybe helps you is that and obtuse angle would be on second quadrant
If you guys are wondering, c is 13.4, Not 13.
rounded off.
@@maknify4538If you use the rounded off one -13- A will be 86.75°. If you use 13.4, A will be 75°, which is the correct answer.
While doing the example (starts around 2m30s), it sounds like you recorded it using a different angle name, then dubbed over "C" in relevant places, and maybe cut a few bits off the original explanation. Am I right?
haha yep i think so, there must have been errors in the script that i had to correct in post
1:39 how did you get 7.92?
You take the square root of 62.7. I know it's late, but still hope this helps.
how did the value of a became 7.92? can you please answer i'm not good at math thank you :)
62.7 is not a, its a^2 so a = √62.7 = 7.92
unsigned thank you 🥺
@@besusbbthank you😂
I get that for SSS solving the angle C first avoids ambiguity but what I don't get is why side c is on the bottom. Why is side c on the bottom? Is there a reason or just arbitrary? I want to put side b on the bottom. How does side c on the bottom help us? If it doesn't I am putting side b on the bottom unless someone smarter than me can justify this orientation. If you don't know why side c is on the bottom it is okay I just don't get it. I mean you swapped angle B and angle C and it doesn't seem instantly familiar. Is the longest side always on the bottom?
The side corresponding to the angle is always opposite to the angle. I guess it could be considered arbitrary, but it is much easier working with this orientation than others. Designating the opposite side of an angle as correspondent is clearer than using one of the two adjacent sides.
I have a test on this in 15 mins
/2 (4.8) (6.3) howw can someone tell mee sorry i can't I'm not good at mathh
so that's it now i'm a man !!!!
Proof to kia koni
I mean how to proove this???
@@sunitaraniggpsbhangu1482 find a video online bruh
when your from school
Goodbye grade 😂