How to use law of cosines for SSS

Learn how to solve for the lengths of the sides and the measures of the angles of a triangle using the law of cosines. The law of cosines is used in determining the lengths of the sides or the measures of the angles of a triangle when no angle measure and the length of the side opposite the angle are both known.
The law of cosines can be used to find the measure of an angle when the length of the three sides of a triangle are known. The law of cosines can be used to find the length of the side of a triangle when the lengths of the other two sides are known and the measure of the opposite angle is known.
#trigonometry#lawofcosines

[@brianmclogan]

I agree, when I teach I remember myself as a student struggling wondering how my professors got from step 1 to step 2. I try to fill in as many steps as possible. Glad it helps you out. Keep up the good work!

[@derekw40]

Are you able to make a video and slow it down a bit for my slow brain.

[@SolarEnergy-n2g]

If you have one obtuse angle your other two angles have to be ACUTE

[@Gooseded]

You actually explain things to your students! My teacher just does the work and expects us to understand what she is doing.

[@davidrodriguez931]

A problem with A lot of my professors is they like to skip the "writing out" steps. i feel like its a better approach to learning if all the steps are written out much like you do in your videos. anyway thanks! your videos help when i cram for a college exam!

[@nutaroo2278]

i had a math teacher who did that and because of it i went from advance student to (idk how else to say so take no offense) normal student.

[@alician2357]

@@nutaroo2278 hate teachers like that. Oh wait I have a teacher like that YAAY😃

[@randalllopez7]

MAKE SURE YOUR CALCULATOR IS ON DEGREES NOT RADIANS, your welcome.

[@hawoidaaja6308]

Thanks

[@AAAAAA-kl7qm]

you're* you're welcome.

[@corinah.cortes3899]

OMG Thank you so Much

[@cattoneclipse5815]

Yes, put your calculator in degree mode.

[@cattoneclipse5815]

If you are using π radians, you would put your calculator in Radian mode. If you are using degrees, you would put your Calculator in degrees. If you are not using Trigonometry, then, it would not matter if you are in degree or radian mode.

[@taylorleishman8114]

"bless you" like a math teacher boss

[@brianmclogan]

+Taylor Leishman : ) happy to help you out!

[@michaeltaddeo3242]

@@brianmclogan Do you run a online math tutoring program? I'm from Canada and online learning is very different than in person learning. It has its ups and downs.

[@spiritoutcast9087]

Wow! Really helpful! I was doing my homework and thus far only came across SAS, and freaked when I saw a SSS problem. Only took 1 minute and a half of your video to help me figure out what I needed to do! Thank you for this helpful video!

[@brianmclogan]

you are very welcome! happy to be able to help

[@chribastion9581]

3:10 "Your other angles have to be obtuse" pretty sure you meant "acute"... thanks for the video, now I can pass my quiz tomorrow lmao

[@brianmclogan]

appreciate it

[@Elijah_Carroll]

These videos helped so much for my test today!!!

[@brianmclogan]

Love it

[@snorky776]

Thank you so much!! My teacher has not been the best at explaining the subject matter to us, and this problem happened to be the exact problem in my book. But was nit thoroughly explained. As to how the SinB was found. You have helped me with so much!! I have been following your videos for a while now, and they are awesome! Thank you!

[@brianmclogan]

snorky776 you are so welcome! very happy to be able to help you out!

[@pool718]

i can't exaggerate how much your videos have helped me understand math, thank you

[@jayceel251]

Thank you SOOO much! I made a mistake when I forgot to divide and I just subtracted and I was so stumped. This helps, I'm so glad you fill in ALL the steps!!

[@cidny5904]

I always view your videos before a math exam these help very much I am very appreciative of your work!

[@Juicyvale14]

If only you were my teacher ....

[@brianmclogan]

happy to help

[@niie1091]

Thanks for making this i just needed to see it worked out and now i think it makes more sense to me it's currently 11:54 and my homework is due tomorrow

[@brianmclogan]

Boom get at it

[@marcusb7468]

I LOVE YOUR TEACHING METHOD SO MUCH!

[@brianmclogan]

You are welcome Marc!

[@pennstater89ad]

Thanks! Big help for my on the demand carpentry trim cut, took many math courses including Trig. at Penn State many years ago but needed a refresher on the LAW OF COSINES. Great Job👍👍!!

[@ssj_209]

Thank you I wish I had you as my teacher

[@saraweisse6367]

Thanks for this video, really. You saved my test for tomorrow. You're a god compared to my teacher. He never explained anything like that, we have to self teach and watch other people's video to learn something. Keep up with the work, it really helps millions of students.

[@brianmclogan]

thank you so much! i really appreciate it and will as always continue to make videos

[@quaadii]

I am a 10th grader and your like the best online math teacher ever. Thanks

[@cattoneclipse5815]

The new school year begins on July 1st, so you're an 11th grader now.

[@quaadii]

@@cattoneclipse5815 no the new school year begins on September 2

[@cattoneclipse5815]

Are you sure the new school year begins in September 2nd? School starts in July or August depending on what calendar you are on. So the school year would begin before September 2nd.

[@lexicast2608]

I've changed my calculator to both degrees and radians and I STILL get errors... can someone tell me what I'm doing wrong???

[@unassumingunaware]

This video saved me on my final and you were the only resource that provided this method!

[@guiitarfreak_]

Helping me prepare for my final. You're a legend mah boi

[@lba_e_ross2152]

These vids are a godsend for quarantine! I wish you were my trig teacher

[@brianmclogan]

I am here to help. Let me know if I can help you out in anyway

[@Cmonbruh660]

watchin in 2020

[@HIGH3RTRUTH]

@@Cmonbruh660 same here

[@randomgirl9073]

@@Cmonbruh660 2021 hehe

[@elizard13]

If only I could’ve discovered his channel at the beginning of this school year, I would’ve actually passed my tests

[@brianmclogan]

well you found me now!

[@danielwalker2381]

I’m in honors algebra II but have now forgotten this :( this is helping a little

[@princessnicolebangoy5984]

Hello, how did you get the 116.80 did you multiply or divide it?

[@jasonmendries4822]

Someone give this man a Cookie!!! Good show jolly good show!

[@brianmclogan]

Jason Mendries thanks

[@coupleocards]

how did you get 41.12 for A every time it says 0.65

[@activ3oli999]

Same you figure this out yet?

[@miguelwimbish7855]

Man, your videos are awesome. Thanks for being a big help.

[@brianmclogan]

You are very welcome!

[@shelbidrumm4816]

Thank you so much! Your videos and explanations might save my math grade yet haha it's our teachers first year teaching pre-calculus and she is not doing good at explaining so far, and its almost time to graduate haha Thanks again!!

[@brianmclogan]

+Shelbi Drumm congrats to you, keep up the hard work and happy I am able to help you out

[@80_eighty47]

thank you so much, im trying to do online courses for geometry and they did such a horrible job at explaining this. Thank you so much!!!

[@brianmclogan]

happy to be there for you, keep up the hard work

[@marianarad63]

Thank you!! i wish i had you as my teacher..

[@raphaeltumate]

Good

[@mondolawrancearmba]

Very impressive 👍

[@iqofbacon6039]

Thank you! Helped me understand more.

[@brianmclogan]

you are very welcome! happy to help

[@simpleman283]

I only thought I was stupid, now I know I am.

[@ekramup7340]

Nice

[@kevingardner2504]

Thank you so much. That makes things so clear!

[@brianmclogan]

awesome! happy to be able to help you out!

[@ianbellpepper]

this man is a hero

[@deformedreynard7493]

I forgot I could plug in the bsquared in the beginning, so I don't need to use a different formula, thank you very much I understand now 👍👍👍👍

[@brianmclogan]

awesome! happy to help

[@圣安地列斯]

Thank you sir. Now I can retake my test which I failed on. .

[@jadentanner1471]

what if i get domain error?

[@mrdillonc1]

You are great! I’m just stuck on how to get A or C after getting B!

[@brianmclogan]

you can do it!

[@jcinaty89]

Great explanation! Thanks

[@brianmclogan]

you are very welcome!

[@olliejones2060]

Wow that cleared that up. Thanks

[@brianmclogan]

You are very welcome!!

[@BiggestJim667]

Once again saving me math grade

[@shrirajreddy9516]

I learned this differently, but thanks for the tip!

[@brianmclogan]

you are very welcome!

[@daul_bae]

3:09 *acute

[@brianmclogan]

yah

[@kellywyatt4024]

does anyone else notice the "duh hello" at the top of the whiteboard?

[@brianmclogan]

it is my sound check, some videos you can hear it

[@ZiongraceDorado]

Is the formula constant except the cosB?

[@marcoabarca1267]

thank you so much you helped me with my online class

[@brianmclogan]

awesome! happy to help

[@PdrittleStar]

When I type inverse it says error

[@kirosaki]

sir so you subtracted 361 with 260 and it equaled 101 if the 101 is also negative what shouuld i doo?

[@yasminhimsieh6490]

crazy how my brain still doesn't understand any of this after watching this 5x through and my professor explaining it the same way,,, trig isn't for me

[@6c15adamsconradwilliam3]

I just subscribed. Can you do a video of simular triangles？

[@brianmclogan]

search "#similartriangles mclogan"

[@brianmclogan]

happy to have you, find the videos?

[@m1v1per95]

That is the most math teacher way of writing a B I've ever seen

[@jambi2118]

hey brian can you help me no matter how many videos i watch i still dont understand

[@iselazavala2233]

For this topic specifically?

[@AdilQuamar]

How did you know what the cosine of B was in the beginning?

[@brianmclogan]

I did not know what it was, I solved for it using the law of cosines, I decided to solve for B rather than the other angles because it was across from the largest side, you will want to always do that to avoid the ambiguous case

[@AdilQuamar]

Oh no, sorry, my wording was wrong. What I meant was how did you know what B was, like the angle B. You substituted cos(13) into the formula and I wanted to know where that 13 came from.

[@chribastion9581]

lmao, it's not a 13, it's the letter B that looks like a 13

[@AdilQuamar]

Chribastion oh haha that makes sense

[@torudro8022]

thnx pimp

[@ktmamales408]

please enlighten me.. c- the longer side should be hypotenuse? which is 19?

[@harrisondougherty3086]

“Hypotenuse” is the longest side for right triangles only, and is directly across from the 90 degree angle. In this case this would just be the longest side of the triangle.

[@DaveyyBabiiee]

I soooo love you so much bro !!!!!!!!!!

[@brianmclogan]

haha just happy to help

[@tin6774]

+Mr. McLogan's Math Channel ty man

[@SirDinzhi]

4:14 how did your answer became 41.12? Mine came out 0.6576

[@samarthverma4289]

After getting 0.6576, you do Inverse SIN of 0.6576 and you should get around 41.12

[@ArvizuTX]

Why do you subtract 260 from 361?

[@Xilosphere]

Why does this formula not work if using a^2 = b^2 + c^2 - 2bc CosA ?? My calculation for angle A was 1.6198

[@brianmclogan]

+Novakira Sato it should make sure your calculator is set to degrees not radians

[@sorte7171]

Bruh at this point ur literally my teacher

[@personperson468]

thank u

[@Adi02]

If you start using SSS LOC, don't you need to complete it using LOC isntead of LOS

[@sydn2698]

Can you subtract the 224 to the 260?

[@brianmclogan]

no because it is being multiplied

[@sydn2698]

Brian McLogan Ah, by the cos(x) I see...

[@SolarEnergy-n2g]

If you have one obtuse angle your other two angles have to be ACUTE

[@francicianni7731]

How do you do the inverse cosine on a calculator

[@brianmclogan]

2nd cosine for most calculators

[@keokpala8562]

a professor said ure not supposed to use law of cosine then law of sines,either one or the other

[@brianmclogan]

You can you just have to be careful for the ambiguous case. So you have to safeguard yourself from that by finding the largest angle first or second

[@tywick6166]

@@brianmclogan I am confused as to how you figure out whether or not to be concerned about the possibility of a second solution. Sadly, its 2am the night before my exam, and theres a 100% chance that you wont reply in time, so in essence, I dont care any more. Cheers

[@cofieleven]

what if your hypotenuse IS NOT your longest side?

[@brianmclogan]

it always is for a right triangle

[@cofieleven]

Thank you Brian, but my question was in regards to a non right angle triangle

[@X-Rayvier]

Cofi Annon Only right triangles have a hypotenuse.

[@Jayyxvina]

Wait so you put inverse sin in after you put .........÷19

[@brianmclogan]

yes

[@rockymalabananserrano9955]

when i press “14sin116.80÷19 the result is 0.6576 or 0.6577 when its rounded off

[@brianmclogan]

type it in one at a time if using a graphing calculator

[@brianmclogan]

make sure to follow the order of operations

[@lilyakydd9507]

Does anyone know what to do if it's a right angled triangle???

[@ms-dosguy6630]

your doomed!

[@nutaroo2278]

anyone else notice the expo marker is red but its cap is green....

[@brianmclogan]

All day

[@indiamillender6213]

WOULD U TELL ME HOW U GOT 13? AS THE COSINE

[@brianmclogan]

where do you see 13?

[@indiamillender6213]

for the cos B

[@hypercubemaster2729]

He didn't. He wrote that cosB=-0.4509. I got pretty much the same thing; cosB=-0.450892857.

[@DokOps1]

Lost me at 2:45

[@axd2102]

W TEACHER W LIFE W WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW

[@tryfialexandris3715]

im in year 4 and i understand

[@shanestewart9045]

Good try

[@arhamahmed3942]

i miss 2013.

[@marwaawwad2079]

did anyone notice how at 4:20 he said shut up

[@brianmclogan]

haha

[@laurinmeier4045]

Duh Hello!

[@antt4873]

seanie is getting mad!!!

[@brianmclogan]

Always

[@ohmcodes]

Duh Hello!