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/sci/ - Science & Math

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6896794 No.6896794 [Reply] [Original]

How do I quickly memorize trigonometric substitutions, identities, and common values quickly? My test is on monday.

>> No.6896800

Draw the 2 triangles it takes less than a minute.
memorize sin^2(x)+ cos^2(x) = 1, divide that by cos^2(x) or sin^2(x) depending on what you need then manipulate.

>> No.6896801

>>6896800
>Draw the 2 triangles it takes less than a minute.
Care to elaborate? I never paid any attention in trig class....

>> No.6896802
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6896802

>>6896794

>> No.6896807

>>6896801
You have the triangle with base and height equal to 1 with hypotenuse of sqrt(2), and that will get you values of anything with the angle 45.
Then you have the 1,2,sqrt(3) triangle with 2 as the hypotenuse, that will give you values for angles with 30 and 60 degrees.

>> No.6896810

>>6896807
OK, that seems simple enough. What about trig identities?

>> No.6896828

>>6896810
you make a lame thread asking for 10th grade math help. ok. somebody gives you a great answer and you ignore it? :(

>memorize sin^2(x)+ cos^2(x) = 1, divide that by cos^2(x) or sin^2(x) depending on what you need then manipulate
that is a better explanation than any teacher will give you TBH
if you can memorize the Pythagorean theorem and apply it to triangles with a hypotenuse of 1 (i.e. anywhere on the unit circle) then you can manipulate in a simple manner to get almost all of the trig identities

the double and half angle identities are a little harder

>> No.6896921

if you have a ti-84 or higher, goto create a new program (on the calculator) and insert all your notes and formulas so you don't have to memorize them.

>> No.6896949

>>6896921
>pre-calc and calc
>not banning calculators

>> No.6896988

>>6896807

Great explanation here for OP

>> No.6897066

>>6896794
Write them down on a small piece od paper m8

>> No.6897091

>>6896794

http://www.sosmath.com/trig/douangl/douangl.html

There you go. I used this site a very long time ago to remind me of trig identities for calc.

If you do problems regularly this shit becomes common knowledge.

>> No.6897161

Not OP, and only slightly related, but i'm about to finish Calc 4, and I still get sine and cosine of 30 and 60 degrees mixed up all the time.

It's also embarrassing how long it takes me to convert the two into radians as well.

>> No.6898494

>>6896828
If you took Calculus II in 10th grade, good for you.
sin^2(x) + cos^2(x) = 1
How do I manipulate that to giving me the other identities?

>>6896921
Graphing calculators aren't allowed.

>>6897066
Cheating is bad.

>>6897091
I believe double/half angle formulas will be provided.

>> No.6898502

Use anki or method of loci

>> No.6898508

>>6898494
look up eulers identity and 2D rotation matrices.

>> No.6898511

>>6898494
Divide by the square of sine. Boom, cotangent cosecant equivalence. Divide by square of cosine for tangent secant equivalence.

Half and double angle can be derived from sum and difference identity, and vice versa (if I remember right). Just break 2 theta into theta plus theta.

Honestly your a lucky bastard if they're even giving you that much. When I took calc 2 we were only given the antiderivatives of the inverse trig functions.

>> No.6898518

>>6898508
>hey look guys, I took intro to complex variables and wanted to show how much smarter I am than OP
>:^)

>> No.6898521

>>6898508
Haven't learned these yet.

>>6898511
The teacher said the Half Angle formulas would be provided because he didn't have them memorized.
We have to memorize inverse trig stuff though...

>> No.6898525
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6898525

>>6898518
>took intro to complex variables
nah, i didn't. buddy of mine showed me when i asked for trig tips. really helped out, so i thought i'd pass it on.

not everyone is an elitist out to make others feel inferior, anon. you should have more faith than that.

>> No.6898537

I also believe there will be Disk/Washer method on my test tomorrow... Are there any good review websites for disk/washer practice?

>> No.6898599

>>6898518
>thinks that eulers identity is hard to use
I can't remember formulas for shit so when i used to have to use double angle formulas i'd try and re-derive them using triangle lengths and axis rotations. Later on i realised if I just messed with Euler's formula for 2 second I had all the double angle formulas come out instantly. It's extraordinarily easy... all you need to remember is that when you multiply "x" to the power of "a" by "x" to the power of "b", the result is "x" to the power of "a + b".

>> No.6898605

>>6898537
you're HS calc class does integration? that's pretty cool actually.
this is a link my calc teacher gave to me, it's actually incredibly informative. I had the cheat sheets printed out (not for cheating, for quick organized access to key ideas) and referenced those a lot.
http://tutorial.math.lamar.edu/

remember that when rotating around y-axis using washer method you're integrating with respect to y-axis, and using shell method you are integrating with respect to x-axis

another good thing to do is buy an older version of a different calc book for like $3 and boom you have a whole new set of practice problems with answers. And a differently worded explanation for any concept you're struggling with.

>> No.6898610

>>6898605
No, I'm a college freshman. I took AP Calc AB (basically Calculus I) in high school so I'm doing Calculus II right now.

>> No.6898643

>>6898610
oh, I was being nicer because I thought you were in 10th grade and doing this stuff

bro you took ap calc and you need to be spoon-fed how to derive the basic trig identities from sin^2 + cos^2 =1? weakkkk

/dickmode

another tip i have is to make a cheat sheet as if you were going to cheat for the test. Like take 1 page of paper and fit everything you would want to know, all the key concepts, formulas, identities, and examples of problems which are similar to those on the test.
Obviously you aren't going to use it to cheat but i find that the exercise of doing that and really examining everything i need to know and getting it together like that really helps me

>> No.6898646

>>6898605
>another good thing to do is buy an older version of a different calc book for like $3 and boom you have a whole new set of practice problems with answers. And a differently worded explanation for any concept you're struggling with.

This. undergrad STEM stuff really hasn't changed in the last 80 years. old books actually read like books instead of stereo instructions. highly recommend.

>> No.6898658

>>6898643
>another tip i have is to make a cheat sheet as if you were going to cheat for the test. Like take 1 page of paper and fit everything you would want to know, all the key concepts, formulas, identities, and examples of problems which are similar to those on the test.

>not having these in your little book
>not autistically carrying your little book around 24/7

>> No.6898891

>>6897161
>CALC 4 AHAHAHAA
please be b8

>> No.6898920

>>6898494
> calculus 2
> doesn't know precalculus level trig

>> No.6898946

>>6898658
>tfw you have a little book with reference notes

>> No.6898962

>>6898891

>What are ODE's/PDE's

>> No.6899045

>>6896794
learn intutively, never memorize

it's too late for either, cram and try not to fail

or just fail

faggot

>> No.6899117

>>6898962
>ODE's/PDE's
ODE's/PDE's what? Are you going to finish your sentence?

>> No.6900477

>>6896794
withdraw