The Law of Cosines

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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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Опубликовано:

13 окт 2024

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Комментарии : 94

@Clarice679 9 месяцев назад

tysm! i fell asleep in class and this was our lesson for today. super helpful.

@Jbnfmshhwbbe1 4 месяца назад

Maybe sleep outside of class?

@Mousedahbidoof 4 месяца назад

@@Jbnfmshhwbbe1 wow cool idea, definitely worth trying, I generally sleep in class and study outside

@dartheater7348 3 года назад

I'm currently failing a test on this

@sebastianszekely3400 2 года назад

bro i got a test tmrw on this.. and i'm just learning now

@strangermadness4208 Год назад

I have a test on this, buts it's in the next 2 hours

@dnola2053 Год назад

I hope you got better

@jojoishighagain Год назад

Same LMAO

@jorgelorenzoenjoyer Год назад

Im having an exam where Ill probably have to explain how to get thos😀

@loriecannon8493 4 года назад

I love the intro

@mark760 3 года назад

Same

@JimJesterMayuyo 3 года назад

Same hahaha

@kristopheralexis9911 3 года назад

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!

@jamaristetson1238 3 года назад

@Kristopher Alexis instablaster =)

@blueberrypi4196 3 года назад

@@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

@divyasharma8372 6 лет назад

Great explanation

@habibaelhadad1000 3 года назад

i like your smart way of teaching professor dave

@editsblazing 8 месяцев назад

Thank you, Professor. Dave!

@stevkohudran 2 года назад

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.

@scxrpion3828 Год назад

Long advance

@av3rymac730 Год назад

I got the same answer. All of my answers were different than his. I have no idea why.

@shanveesood8704 Год назад

Maybe your calculators were in radian mode? Or degree mode?

@manacchiie8323 Год назад

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

@manuellakasiama6993 3 года назад

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 ?

@manuellakasiama6993 3 года назад

I see you've only used 2 of the formulas so how to solve with b^2=a^2+c^2-2ac cos B?

@JimJesterMayuyo 3 года назад

Same method

@dangerouslydubiousdoubleda9821 2 года назад

you repeat the same steps just with different value

@JM-xz4ur 2 года назад

oh my god you literally saved me thank u sm!!!

@bravo3541 2 года назад

At 2:49 you say "just divide". Where does division come from? Thanks. very helpful.

@charlie_0757 Год назад

When we move 2ab to the other side, it goes from multiplication to division.

@0xAldehyde Год назад

This is transposing method .

@NJ-co6qs 6 лет назад

nice video and good graphics how do you edit these videos 👍👌

@ProfessorDaveExplains 6 лет назад

adobe premiere and after effects!

@NJ-co6qs 6 лет назад

Professor Dave Explains : awesome and thank you

@sumasree7101 6 лет назад

Plss.. upload videos of physics...

@1hoursongs50 6 лет назад

Yeah

@ProfessorDaveExplains 6 лет назад

dudes i did two entire physics series, classical physics and modern physics!

@bryanlim7355 6 лет назад

Professor Dave Explains he means do videos on Electrical or mechanical engineering courses!

@manuellakasiama6993 3 года назад

may I know how you got cos C = -0.157

@edson_winner 2 года назад

Got subscribed! Great explanation.

@cometolearn8598 3 года назад

How To Add, Sub , Divide And Multiple Degree With Out Calculator

@airhead1430 6 лет назад

Sometimes I don’t know the difference between sine and tangent

@ProfessorDaveExplains 6 лет назад

go back to the earlier trigonometry tutorials for review!

@bryanlim7355 6 лет назад

Professor Dave Explains what was your field of study in university? What course did you study last time? What type of student are you?

@ProfessorDaveExplains 6 лет назад

i studied chemistry in undergrad, now i'm wrapping up a masters in science education

@bryanlim7355 6 лет назад

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

@kunasagaran5933 5 лет назад

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.

@truthbetold89 3 года назад

Thank you sir

@sw4gc0r36 5 месяцев назад

you helped me so much!!!

@manuellakasiama6993 3 года назад

how did you get a= 7.92

@sebastianszekely3400 2 года назад

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

@ceegae1670 Месяц назад

Take the square root of both side to get rid of the square on a

@fsmgaming936 Год назад

thank you!

@hockeyfan2115 2 года назад

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

@nikolaivii5766 4 года назад

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?

@ProfessorDaveExplains 4 года назад

haha yep i think so, there must have been errors in the script that i had to correct in post

@abiasiddiqui9428 4 года назад

Plz upload a video about sine and cosine of obtuse angles

@ProfessorDaveExplains 4 года назад

watch my whole trigonometry playlist it's all in there

@abiasiddiqui9428 4 года назад

@@ProfessorDaveExplains sadly can't find:-(

@ProfessorDaveExplains 4 года назад

home page, scroll down to mathematics section, scroll right for trigonometry

@abiasiddiqui9428 4 года назад

@@ProfessorDaveExplains prof could u kindly just tell me the vid name or any hint I'll be grateful

@aveinmovil 2 года назад

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-cqIZue-plBI.html You can go from here, a hint maybe helps you is that and obtuse angle would be on second quadrant

@potatomudkip 3 года назад

done with trig after 2 weeks, yey

@phosphorus3380 3 года назад

Thanks a lot

@palakmotivation6695 Год назад

I'm from India....but I study from this video 🤩🤩

@estebanadrianeb.7469 4 года назад

how did the value of a became 7.92? can you please answer i'm not good at math thank you :)

@besusbb 4 года назад

62.7 is not a, its a^2 so a = √62.7 = 7.92

@estebanadrianeb.7469 4 года назад

unsigned thank you 🥺

@spencerward3102 Год назад

@@besusbbthank you😂

@FredrikSvensson1979 2 года назад

You bear a slight resemblance to 66Samus, the death metal drummer. Emphasis on slight.

@JaylahBedford-nm7kj Год назад

1:39 how did you get 7.92?

@kristerskonosonoks9480 19 дней назад

@@Belmont1714yes i was confused as hell thank you

@mochigyu3755 3 года назад

/2 (4.8) (6.3) howw can someone tell mee sorry i can't I'm not good at mathh

@habibaelhadad1000 3 года назад

thanq

@sunitaraniggpsbhangu1482 6 лет назад

Proof to kia koni

@sunitaraniggpsbhangu1482 6 лет назад

I mean how to proove this???

@sebastianszekely3400 2 года назад

@@sunitaraniggpsbhangu1482 find a video online bruh

@Jxfak Год назад

thank you papi

@josephmalone253 3 года назад

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?

@hunkymunky1704 2 года назад

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.