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Using sum and difference formula to find the exact value with cosine
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- čas přidán 11. 01. 2016
- 👉 Learn how to evaluate the cosine of an angle in radians using the sum/difference formulas. To do this, we first express the given angle as a sum or a difference of two (easy to evaluate) angles, then we use the unit circle and the Pythagoras theorem to identify the angles and obtain all the needed trigonometric function values of the angles. When we know the trigonometric function values of the two angles to be added or subtracted, we can apply the sum and difference formulas to evaluate the cosine of the given angle.
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Organized Videos:
✅ Sum and Difference Formulas
• Sum and Difference For...
✅ Evaluate Sum and Difference Formulas from a Triangle
• Evaluate Sum and Diffe...
✅ Simplify an Expression using Sum and Difference Formulas
• Simplify an Expression...
✅ Write the Expression as a single function | Sum and Difference Formulas
• Write the Expression a...
✅ Verify Identities using Sum and Difference Identities
• Verify Identities usin...
✅ Evaluate Tangent using Sum and Difference Formulas
• Evaluate Tangent using...
✅ Evaluate Cosine using Sum and Difference Formulas
• Evaluate Cosine using ...
✅ Evaluate Sine using Sum and Difference of Two Angles
• Evaluate Sine using Su...
✅ Solve Equations using Sum and Difference Formulas
• Solve Equations using ...
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#analytictrig #brianmlogan
That feeling when he uses the exact problem you've been given. 🥰
ergo when your teacher is just as lazy as you are :D (you impersonal)
Never have I more related to a 4 year old comment
SAME
Dude, I'm in college Trig right now and I am STRUGGLING. My professor doesn't explain the logic behind anything and the textbook videos aren't much better. Your videos are the reason I've understood most of what has been taught in the class. I can't thank you enough.
exact same boat
@@huntersage4007 same lol. Should not have taken it online!
Bro I’m in high school taking this😭😭
@@DrPeppaa I feel that! Test in an hour :(
@@ethanhayes3584 best of luck to you brother, hope you passed 👍🏽
lol nooo dont loose your patience with that person. i needed that answer example ti finish my homework lol.
Dude frrrr lmao
Same😭😭😭😭
I sat in my chair for 3 hours trying to figure this out.. 1:35 ... holy crap! Thanks!
There are no bad questions from someone whose never seen it, wish he didn't sorta snub her, that deters people from asking questions in the future
great point, I always welcome questions from students, not sure the context of this lesson or question. Sometimes when I notice students not paying attention but then asking questions when everyone else was paying attention knows, I get frustrated. Not sure if that was the case, or I could have just had a bad day.
Happens to the best of us
it was a stupid question anyway
@@lucasargandona4658 oh yeah yeah
yeah that was why I sucked at math in hs and middle school... too afraid to ask questions cuz I didn't want to get called out on
For anyone wondering how he got the (pi/3 + pi/4)
How I got it is pick a point on the unit circle, such as pi/3 or pi/4 (it helps to memorize the unit circle) and minus that by 7pi/12.
So I'll pick pi/4 because from memorizing the unit circle I know that we can subtract and get the 2nd value
1.) 7pi/12 - pi/4
1a.) pi/4 -> becomes 3pi/12 we need equal denominators to subtract from 7pi/12
2.) 7pi/12 - 3pi/12 = 4pi/12
2a.) simply 4pi/12 and you get pi/3
3.) you can verify that the values
pi/4 pi/3 and by adding both and you will get 7pi/12
I appreciate brian Logan saying not to worry about getting the 2 sums or difference to get the ball rolling but eventually this will catch up with you and you will have a gap in your knowledge. I can't think intuitively like that in math so I find this sort of algorithmic way to find the values.
He is a wonderful prof, makes life easy. Makes solving math problems piece of cake :)
happy to be able to help you out!
*piece of pie
Exam tomorrow and you helped me understand this type of problem thank you 😅😅
Perfect explanation. Thank you.
you are very welcome! happy to help
YOU MAKE IT EASIER! THANK YOU SO MUCH!
you are very welcome!
in 10th grade in highschool and my teacher in algebra 2 sucks. this dude helps so much. i know this is 8 years later, but thank you 🙏🙏
you're a lifesaver !! thank you so much
you are very welcome!
im curious what level you are teaching at?? i wish my professor would be this thorough on explanations but we're always strapped for time.. she just seems to blaze through topics.. and right as i make sense of it, she moves to the next topic. I
really appreciate all the effort and time it took to make this channel tho .. youve helped me immensely in my trig class.. Brian McLogan
I'm learning this in dual credit highschool, so college level maybe?
Highschool level
Found the video on radians! Great job! Im not sure if you are a teacher or professor, but either one you teach very well!! 😬😅
thank you, yes I teach high school
Brian McLogan You’re welcome!
THIS MAN IS A GIFT FROM GOD BLESS YOU GOOD SIR
Thank you!
How will you do cos(Pi/16) ? It’s a decimal value so it isn’t on the unit circle
is there a way to memorize the subtraction/addition formulas for sin/cos/tan?
write them a lot
Brian McLogan 😂😂😂😂😂😂
Can we convert that from rad to degrees and solve using trig sum or difference formulas??
Say: cos(60 + 45) = cos60cos45 + sin60sin45 and then use the special triangles??
My test is tomorrow so you probably wont see this on time :)
That's what he did but his trials are in radians
What if it is negative? Cos-(7π/12)?
can you show how to solve it by converting to degrees please?
I still dont get it
زۆر سوپاس مامە گیان، ڤیدیوێکی بەسوودە
Thanks for this but plz make a video of sin2 360.
Why am I a junior in high school learning this 🥺
Didn't understand where the addition terms came from and you helped me big time
awesome! happy to help
why did the sign chage though?
The sin identity gets to keep the same sign, but for the cosine the sign changes, that's the way it is but i don't know the reason.
Never mind it works
Lot of videos on easy problems. Why no video on hard problems - e.g. how to calculate sin π/17 ?
Heres an easy way to find the two additions if you have to:
If you had 7pi/12 like in this example, just do
Api/12 + Bpi/12 = 7pi/12
You have to find numbers that are divisible by 12 that also add upto 7, so its a bit of mental math here but its never too bad
I know 2pi/12 and 5pi/12 add upto 7pi/12 but 5pi/12 *isnt divisible by 12* so dont use that pair.
I know that 3pi/12 and 4pi/12 equal 7 and both numbers are also divisible by 12 so it works.
Simplify and you get pi/4 and pi/3 which are your special triangles and useful for finding exact values
Eeeeyeaah next video
its actually 105 degrees, not 95 degress as he said
I got scared bc he said my name when he did the U and V bc i dont do them lol.
Your name is Justin?
@@lucasargandona4658 Maufstin
your thumbnail looks funny xD
it does, haha
Plzzz sin 2tita÷5
I think your pi/3 should be 3pi/8 and your pi/6 should be pi/8 in your sketch.
India
Do you get paid extra for these videos?
nope just a little from the ads, I just love helping and hearing from students all over the world, makes everything worth it
he has more views and subs than some people who do it full time i’m sure at least now he makes a lot off of it
you lost me at the start
Ha lol
If I didn't have a clue of math, I probably wouldn't understand this teacher. Lmao! Just saying.
im in 8th grade doing this
Kylestyle16 Im a senior in high school and I dont get this lol. Good Luck
im a freshman in college and I don't know what Im doing lmao
I’m a 11 grader and don’t get this 😂
I'm a junior in college studying this at 6am so best of luck to ya girl
It seems like he have no patience and a nasty sarcasm. He should be happy someone is asking questions and wants to learn no matter how many times you've repeated it. My opinion.