#help-28

1 messages · Page 183 of 1

tacit siren
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Show the set D \subset C(A, R^m) of functions with norm less than 1 is closed and bounded but not compact

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Hint says to show a sequence of D is not equicontinuous

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Then use a modified version of arsela-ascoli for R^n

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f_n(x) = x^n for A= [0 1]

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Next

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Suppose $A$ is a compact subset of $R^m$, $f:R^m \rightarrow R^m$, and $\mathscr{B} is a subset of continuous functions from $A$ to $R^m$ such that for each$ x_0$ and $\epsilon$, there exists a $\delta$ such that $d(x, x_0)< \delta$ implies $d(f(x), f(x_0)) < \epsilon$ for all $f$ in $\mathscr{B}$.

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Prove Script B is equicontinuous

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Ok so

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I'm guessing I just take all the B(x, delta_x)

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And take a finite cover

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Wait hm

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Guess there's more to it than that

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Ok I dunno

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<@&286206848099549185> i could use a hint im kinda tired

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Uhh the current problem is the message at 10:06 AM

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West coast time

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Suppose $A$ is a compact subset of $R^m$, $f:R^m \rightarrow R^m$, and $\mathscr{B}$ is a subset of continuous functions from $A$ to $R^m$ such that for each $ x_0$ and $\epsilon$, there exists a $\delta$ such that $d(x, x_0)< \delta$ implies $d(f(x), f(x_0)) < \epsilon$ for all $f$ in $\mathscr{B}$. Prove that $\mathscr{B} $ is equicontinuous.

I figure we cover $A$ with $B(x, \delta_{x, \epsilon})$ and take a finite subcover of that, but im not sure where to go from there

glossy valveBOT
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992HallucigeniaEnthusiast

tacit siren
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Gonna take a nap brb

full forumBOT
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@tacit siren Has your question been resolved?

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full forumBOT
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hardy vigil
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I need help
quick dm me
grade 7 linear equation and also inequalities

wise wyvern
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Why can't a game developer do grade 7 linear equations?

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Also, why dm? Just post it here.

somber niche
shy shore
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maybe the game isnt math related.. somehow

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you'd think hp systems and such would require nearly every game to be math related

somber niche
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Is it possible for a computer game to not be math related in terms of development?

wise wyvern
shy shore
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no simple arithmetic? absolutely not, no complex functions, probably

somber niche
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Like, utilizing at least 1 algebraic expression in the code for example

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but then logical statements also fall in math

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hmm...

shy shore
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rendering the game would take math, i assume we ignore that factor

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is num1++ allowed? are all forms of arithmetic allowed?

torn jolt
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Y'all arguing over what?

shy shore
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seems like bored discussion

torn jolt
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Damn what you upto

wise wyvern
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More like, I already know the idea of game development. And what it does use, is infact mathematics. I'd call it mathematics all day. So nothing left to discuss lol. But this isn't the right channel for it, so...

shy shore
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very good point

hardy vigil
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  1. Preeta watches an ant and a beetle crawl in a hole in the ground. The beetle is 3/4 inch below ground level. The beetle climbs 1/3 the distance the ant is below ground level. The beetle is now 2 1/2 inches below ground level.

(a) Let x = the position of the ant relative to ground level. What equation can be written to solve for x?

(b) Solve the equation from Part (a). Show your work.

(c) What is the distance between where the ant is and where the beetle is? Answer the question in a complete sentence. Show your work.

full forumBOT
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Show your work, and if possible, explain where you are stuck.

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What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
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@hardy vigil Has your question been resolved?

hardy vigil
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<@&286206848099549185>

west mist
hardy vigil
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My questionn

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Preeta watches an ant and a beetle crawl in a hole in the ground. The beetle is 3/4 inch below ground level. The beetle climbs 1/3 the distance the ant is below ground level. The beetle is now 2 1/2 inches below ground level.

(a) Let x = the position of the ant relative to ground level. What equation can be written to solve for x?

(b) Solve the equation from Part (a). Show your work.

(c) What is the distance between where the ant is and where the beetle is? Answer the question in a complete sentence. Show your work.

hardy vigil
west mist
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Ok am gonna see

hardy vigil
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i have only done till

3/4 + 1/3x = 2 1/2
3/4 + 1/3x = 5/2

west mist
# hardy vigil can u help

Let's solve this problem step by step:

Given information:

  • The beetle is 3/4 inch below ground level.
  • The beetle climbs 1/3 of the distance the ant is below ground level.
  • After climbing, the beetle is 2 1/2 inches below ground level.

Let x be the position of the ant relative to ground level.

(a) Equation to solve for x:
The beetle starts at 3/4 inch below ground level and climbs 1/3 of the distance the ant is below ground level. After climbing, the beetle is 2 1/2 inches below ground level.

So, the equation can be written as:
3/4 + 1/3x = 2 1/2

(b) Solve the equation:
To solve the equation, we need to find x that satisfies the equation:
3/4 + 1/3x = 2 1/2

Convert 2 1/2 to an improper fraction:
2 1/2 = 5/2

Now, solve for x:
3/4 + 1/3x = 5/2
1/3x = 5/2 - 3/4
1/3x = 10/4 - 3/4
1/3x = 7/4
x = (7/4) * 3
x = 21/4
x = 5 1/4 inches

(c) Distance between the ant and the beetle:
To find the distance between where the ant is and where the beetle is, we calculate the absolute difference between their positions:
Distance = |x - 3/4|
Distance = |5 1/4 - 3/4|
Distance = |5 - 3| = 2 inches

Therefore, the distance between where the ant is and where the beetle is 2 inches.

west mist
# hardy vigil i have only done till 3/4 + 1/3x = 2 1/2 3/4 + 1/3x = 5/2

Let's continue solving the equation:

3/4 + 1/3x = 5/2

First, let's get a common denominator for 3 and 4 on the left side:

3/4 + 1/3x = 5/2
3/4 + 1/3x = 10/4

Now, combine the fractions on the left side:

3/4 + 1/3x = 10/4
3/4 + 1/3x = 10/4

Now, subtract 3/4 from both sides to isolate the term with x:

1/3x = 10/4 - 3/4
1/3x = 7/4

Multiply both sides by 3 to solve for x:

x = (7/4) * 3
x = 21/4
x = 5 1/4 inches

So, the position of the ant relative to ground level is 5 1/4 inches.

hardy vigil
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??????

west mist
hardy vigil
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so this is the answer?

west mist
hardy vigil
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sure?

west mist
hardy vigil
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cool

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thx man

west mist
shy shore
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<@&268886789983436800> this cant not be chatgpt

west mist
spiral vigil
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what is wrong with you

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do you think we can't go to chatgpt ourselves?

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provide value or leave.

shy shore
hardy vigil
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we need human help

shy shore
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but no chatgpt

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also dont give the answers thx

hardy vigil
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.reopen

shy shore
# hardy vigil can you help

since youve gotten the answer from chatgpt i think you can follow along, do you have any specific questions about the solution i can help you with tho

hardy vigil
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i dont get the answer

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i think it contains an error

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i would like it if you could resolve it

shy shore
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im sorry but i cant just provide the answer for you, i could try guiding you im not exceptional at helping people though

hardy vigil
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no problem just guide me

shy shore
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alright so you have finished a) right?

hardy vigil
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yeah

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3/4 + 1/3x = 2 1/2
3/4 + 1/3x = 5/2

shy shore
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alright, now we can start to solve it, do you know how to solve a linear equation?

hardy vigil
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......

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i know but i am bad

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REAL BAD

shy shore
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its alright, just try to write it step by step and ill try to correct you if you go wrong

hardy vigil
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x = 21/4????

shy shore
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could you write it step by step?

hardy vigil
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3/4 + 1/3x = 2 1/2
3/4 + 1/3x = 5/2
1/3x = 5/2 – 3/4
1/3x = 10/4 – 3/4
1/3x = 7/4

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i did it till here

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i dunno what to do further

shy shore
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do you know how to go from 1/3x = 7/4 to x = 21/4

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or am i misunderstanding you

hardy vigil
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multiply?

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7x3 = 21

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4x1 = 4

shy shore
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yes exactly

hardy vigil
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21/4

shy shore
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for multiplication i recommend using * as it doesnt cause confusing with the variable x

hardy vigil
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k

shy shore
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great so now you have x = 21/4 so you have solved b)

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Preeta watches an ant and a beetle crawl in a hole in the ground. The beetle is 3/4 inch below ground level. The beetle climbs 1/3 the distance the ant is below ground level. The beetle is now 2 1/2 inches below ground level.

(a) Let x = the position of the ant relative to ground level. What equation can be written to solve for x?

(b) Solve the equation from Part (a). Show your work.

(c) What is the distance between where the ant is and where the beetle is? Answer the question in a complete sentence. Show your work.
copying it down for accessibility

hardy vigil
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What is the distance between where the ant is and where the beetle is? Answer the question in a complete sentence. Show your work.

shy shore
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do you have an idea how to approach c?

hardy vigil
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nope

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😦

orchid osprey
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yo

shy shore
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occupied

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or are you here to help?

shy shore
# hardy vigil 😦

alright so how would you go about calculating the distance between for example 2 items where one of them is at 1cm and the other is at 3cm

hardy vigil
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subtract

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but what should i subtract

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???

shy shore
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to calculate the example what do you think the best option is

orchid osprey
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we substract

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the dist would be 2cm

hardy vigil
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how????????

shy shore
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if you subtract the 1 cm from the 3 cm you get the difference between the distances, the difference is the distance between them

hardy vigil
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2

shy shore
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now you can apply that to the distance of the ant and beetle

hardy vigil
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are you talking bout my question or the example

hardy vigil
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we found x

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which is the value of the ant

shy shore
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knowing the beetle is 2 1/2 inch under the ground, and the ant is 21/4, or 5 1/4 inch under

hardy vigil
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and the beetle is 2 1/2

shy shore
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oops yeah

hardy vigil
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so..

shy shore
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now we can use the subtract we used in the example with this situation

hardy vigil
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we would 2 1/2 - 21/4

shy shore
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almost

hardy vigil
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5/2 - 21/4

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or

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21/4 - 5/2

shy shore
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since the 5 1/4 is bigger we subtract the 2 1/2 from that instead,
5 1/4 - 2 1/2

hardy vigil
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21/4 - 5/2?

shy shore
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yes

hardy vigil
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thanks man you are the best!!

shy shore
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np, now just formulate it into a sentence and ur assignment should be completed

hardy vigil
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btw what is ur instgram

shy shore
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i dont have it, why

hardy vigil
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nah just wanted to be friends:)

shy shore
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😂

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idk if i can close this channel could you?

hardy vigil
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.close

full forumBOT
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full forumBOT
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celest zinc
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worthy ginkgo
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what have you tried so far?

celest zinc
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It's now tan(2arcsin(lsinxl+lcosxl))

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If we use tan 2theta

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It becomes complicated

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<@&286206848099549185>

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@celest zinc Has your question been resolved?

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plush egret
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.close @woeful anvil

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can you see this?

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plush egret
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oops

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haha

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.close

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woeful anvil
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only show up as

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suggested

plush egret
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oh weird

vestal meadow
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why is that there?

sudden spear
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New discord feature

vestal meadow
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oh

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I knew they changed it back recently

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didnt know they added new feature

plush egret
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.reopen

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sudden spear
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You probably have to sign up to see all the help channels in here

umbral dome
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use id:customize and select "i need help with math" to get access to all help channels

woeful anvil
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wroked

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@plush egret Has your question been resolved?

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nova topaz
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Is there a quick way to work this out without having to do a lot of working out?

nova topaz
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My first thought is let A be the first matrix. 2 * column 1 of A + x * column 2 of A -3 * column three of A = column 7 of A

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and solve for x

fathom saddle
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I'd just reduce "as much as needed" to get the final answer

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You don't need to reduce the bottom 3 rows. You don't need to include any of the numbers outside of the first 3 columns

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You do want to keep the -13 in the ? spot, and keep track of it, though

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torn jolt
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The first statement is wrong

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For n >= 2 .....

elder cape
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how so?

vestal meadow
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how did you get the last inequality?

torn jolt
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Say n is 5

elder cape
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We r assuming log n to be base 2

vestal meadow
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oh

torn jolt
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Oh

elder cape
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yeah

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is it correct now then? lol

vestal meadow
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i still don't see how the last inequality is true

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@elder cape you gonna explain how you got the last inequality?

elder cape
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I'm figuring it out, one sec

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nvm

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.close

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vital spruce
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i have a vector and an axis

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vital spruce
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how can i get the magantude of the vector on the axis

torn gust
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tropic grotto
#

Hey there! Got a physics question on wave interference

tropic grotto
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This is the question

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and this is our work so far

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Using desmos, we found that the answer should be 2, but we're having trouble finding the answer symbolically

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(that is, that the position should be at 3or 7 meters from the left source, which is 2 away from the midpoint between the sources)

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You can also ignore the "k" part

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The main confusion I'm running into is calculating the phase difference deltaPhi. Honestly the whole thing is really confusing too

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@tropic grotto Has your question been resolved?

tropic grotto
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<@&286206848099549185>

torn jolt
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What would the wave equation for the wave released by source 2 be ?

tropic grotto
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Asin(kx-wt+phi_0), no? But we're taking a picture of the wave at an arbitrary time t, so can't we just get rid of the wt term by assuming we're starting our time at t = 0?

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Though i guess the wt terms would cancel?

torn jolt
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And why phi_0?

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I am not sure about removing w

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Give me a min

tropic grotto
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well technically both waves have the same initial phase, so it wouldn't be phi_0, it would be delta_phi, right?

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that is, the phase difference. Since both waves have the same initial phase, I just assumed phi_0 = 0

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Anyway, that's what I've written on the whiteboard, after dividing out the amplitude

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the issue is I'm stuck on how to represent delta_phi symbolically, since the equation relies on delta_D, which relies on the distances from x to the sources

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So the expression I get at the very end is circular, like its saying "x depends on x"

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Thanks for replying btw, been here a minute lol

torn jolt
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Trying to make sense of what you are saying

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Thought this was going to be easy

tropic grotto
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I wish lol, this has taken me hours

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I mean, if it makes it easier, we could ignore my work and start from the initial question

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The idea is we want to solve the equation 0 = Asin(kx - wt) + Asin(ks - wt + delta_phi) for x, right?

torn jolt
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Yes

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Wait a min

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The wave from the second source is travelling towards negative x axis

tropic grotto
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Yeah

torn jolt
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So it would be kx+wt

tropic grotto
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That makes sense, and would explain why it cancels if we move it to one side and take the arcsin

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So we should be able to get rid of the t term

torn jolt
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What you are saying is right,but will that help us in anyway?

tropic grotto
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It reduces the equation to one variable. Unless we just let t=0, which also takes care of that

torn jolt
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What should be the phase difference ?

tropic grotto
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That's what I'm trying to find

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it should be equal to k times the path difference delta_D

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0 = sin(kx) + sin(kx + delta_Phi)
-sin(kx + delta_Phi) = sin(kx)
-kx - delta_Phi = kx
- delta_Phi = 2kx

torn jolt
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Mb

tropic grotto
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no worries, its a dense problem lol

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does the above look correct to you so far?

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i forget big delta notation lol

torn jolt
tropic grotto
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$$x = - \frac{\Delta \phi}{2k}$$

glossy valveBOT
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Rafzekael

tropic grotto
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there we go

torn jolt
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Oh

tropic grotto
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so since delta_Phi = k*delta_D, and delta_D = |d_1 - d_2|

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we should get

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$$x = - \frac{\abs{d_1-d_2}}2$$

glossy valveBOT
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Rafzekael

tropic grotto
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the issue with this is that both d_1 and d_2 depend on x...

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and that's where I'm stuck

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(also it depends on where you define your orgin which makes things even more confusing lol

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idk lol. this phase difference stuff is hella confusing to me

torn jolt
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Say origin is at source 1

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What would the wave equation be?

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For source 2

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(I don't know)

tropic grotto
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to simplify, sin(kx + delta_Phi)

torn jolt
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Why does delta phi keep showing up

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They said same phase difference right?

tropic grotto
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That's the phase difference between two waves

torn jolt
tropic grotto
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The waves have the same initial phase, but that's different from phase difference

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because they are offset by position

torn jolt
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Man,I am getting confused

tropic grotto
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haha, yeahhhh...me too

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Here's a desmos graph with the actual values

torn jolt
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Sorry for intervening

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This was supposed to be easy

tropic grotto
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Nah, no worries at all! I appreciate any help

torn jolt
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Simple

tropic grotto
torn jolt
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Assumed

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XD

tropic grotto
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hahah, yeah if only lol

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I think I'm missing an equation

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cuz otherwise i feel like i'm really close to the answer

torn jolt
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Ahhh

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Y2 I.e wave from second source

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Is 0 at x equals 10

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We get delta phi from that won't we

tropic grotto
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We can, but the issue is that the question wants us to solve it symbolically first for full credit

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so without any numbers lol

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I suppose we could say it equals zero at x = d...

torn jolt
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I am taking origin at source 1

tropic grotto
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lmao

torn jolt
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Out of my league

tropic grotto
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that's fair

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take care, friend. thanks for the help ^^

#

.close

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deep robin
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deep robin
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Is this correct?

brisk kestrel
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Absolutely corrrct

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But u need to do one more thing

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The surface area for the top is (21x12)-(8x4)

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inland silo
#

how should i proceed with question 2?

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buoyant yew
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buoyant yew
#

How to find the average speed for the whole jounrye?

tiny terrace
#

Average speed is total length travelled over time

#

Average velocity is total displacement over time

desert trout
buoyant yew
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Man you a lifesaver fr

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quaint mortar
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quaint mortar
#

i dont understand how to do this question

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quaint mortar
#

<@&286206848099549185>

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quaint mortar
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<@&286206848099549185>

pallid hatch
#

you can use trigonometry for abd and e.

quaint mortar
#

how tho

pallid hatch
#

for the first one, BC is adjacent to the angle of 40 degrees and the length of the hypotenuse is given (18m). as we have the hypotenuse and are looking for the adjacent we must use cos(θ) = adjacent / hypotenuse. substitute in the values: cos(40) = adjacent / 18 . Now rearrange to have the adjacent equal to 18 * cos(40) = adjacent. This is BD

quaint mortar
#

ahh

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i get it now

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thank you

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lost raptor
#

how would i do this question? I cant seem to apply the approximation

open igloo
#

For a quantity $$Z= AB,$$
$$\frac{\Delta Z}{Z}= \frac{\Delta A}{A} + \frac{\Delta B}{B}$$

glossy valveBOT
#

Sulphur

open igloo
#

(Delta A)/A, for example, is the relative change of A
Similarly for the other things

lost raptor
#

would that make it -1%?

#

but answers say -9

open igloo
#

Yeah coz you have to find change in V, not v

lost raptor
#

so I rearrange to V=v/(kA)

#

and because its a division would it become -5%-(+4%) = -9%?

open igloo
lost raptor
#

okay thanks alot

lost raptor
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@royal kettle Has your question been resolved?

deep robin
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upper flower
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upper flower
#

Hi, sorry I don't know how to use the math bot

#

but I have this problem here

#

I solved this by doing ln to the expression

#

and after simplifying and all I get 4

#

but by doing it the way outlined in the other solution, I obtain e^4, which is the correct solution

#

was just wondering if anyone could let me know how I could get e^4 using the method i solved by (and why)

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unborn pike
#

You are taking ln both sides

#

So let y= the limit

#

So you got lny= 4

#

y= e^4

upper flower
#

yeah that's true

#

guess it was that simple

#

didnt think about other side

#

thanks for your help !

#

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dim pumice
#

"Linearize the function
...
around the point A = (6, 5). Then use it to calculate an approximate value of f(B), where B lies on
distance 0.17 l.e. from A in the direction (8, −15). (Please compare with f(B) calculated with a mini calculator).
Also state the equation for the tangent plane to the surface z = f(x, y) at point A."

dim pumice
#

i dont really get how this is solved

#

i start by putting in A(6,5) into sqrt(228+x^2+y^2) and get 17

viral jasper
dim pumice
#

hmm okay can i not calculate b first by doing a + h?

viral jasper
#

Sure

dim pumice
#

okay then we get (6.08, 4.85) right

#

but then my teacher does f(a) = f(7,5) = 342 + ln(1) * 17 = 342

#

and i dont understand why

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fiery sun
#

How do i solve this

full forumBOT
fiery sun
#

part (b)(ii)

spare dust
#

65

fiery sun
#

How?

umbral dome
fiery sun
#

Based on the argand diagram?

umbral dome
#

yes

fiery sun
umbral dome
#

a purely imaginary number must lie on the imaginary axis

fiery sun
#

Ohh

#

Ohhhhh

#

Since arg(z) = -5pi/9 lies in the third quadrant

#

Yea its -pi/2

delicate patio
#

||+- pi/2 ?||

fiery sun
#

As it has to lie on the imaginary plane?

#

Is it positive or negative pi/2? now

#

Well based on the argument it is in the third quadrant

#

So i assume it is negative

#

??

delicate patio
#

idk cus its purily imaginare it can be positive or negative axis right ?

fiery sun
#

Yea but z = -5pi/9

ashen crescent
#

From i) did you get positive or negative i?

delicate patio
#

my imaginary numbers are not my best so im asking as well

fiery sun
umbral dome
#

well just from the fact that it's purely imaginary it must be either +/- pi/2. and we know that z has a negative imaginary part, therefore its conjugate has a positive imaginary part (which we are subtracting)

fiery sun
#

The qn has alrdy given the argument

#

ohh

#

So its - pi/2?

umbral dome
#

yes

fiery sun
#

Thank you

#

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royal crest
#

Hi I need help setting up this double integral
The double integral of (x-y)DA over the region R who is defined by the inequalties y <= 2x -1, y >= -x, and y <= 4 -x^2

viral jasper
royal crest
#

So where i'm getting at is that the domain of x ranges from 1/3 to (1+sqrt(17))/2?

#

and y is bounded by the 2x- 1 and -x? but I don't think that is correct of the parabola of 4-x^2

gritty robin
#

Can a number 44...41, whose decimal representation consists of an odd number of digits 4 followed by a digit 1, be a perfect square?

#

I need help pls msg me

sullen hinge
gritty robin
#

ah ok

royal crest
viral jasper
royal crest
#

Ohhhh alright that made so much sense thanks

#

c:

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craggy plinth
#

A 9200 USD investment grows to 12000 USD in 4 years. What is the annual interest rate?

craggy plinth
#

So i did 12000 = 9200(1+- r)^4

#

then 12000/9200 = 1.304347826

#

1.304347826 = (1 +- r)^4

#

square root both sides by 4

#

therefore

hallow walrus
#

are you sure it's not simple interest

craggy plinth
#

i get +-1.068681656 = 1 +- r

craggy plinth
#

10th grade math class

#

so listne

hallow walrus
#

so?

#

what does that matter

craggy plinth
#

+-1.068681656 = 1 +- r

#

right

#

so

#

what if

#

R =

#

2.07

craggy plinth
#

because basically

#

if we can have it as -1.068681656

#

= 1 - r

#

we subtract both sides by 1

#

and then divide both sides by -1

hallow walrus
#

that isn't a valid solution

craggy plinth
#

ok

#

so what do we do

hallow walrus
craggy plinth
#

because that's from the original formula

#

A = A0 (1 +- r)^t

hallow walrus
#

$\frac{12000}{9200}=(1+r)^4$

glossy valveBOT
#

kheerii

craggy plinth
#

t being years in some cases, such as this

craggy plinth
hallow walrus
#

you're not given any information about how the interest compounds

#

whether it's per annum, twice per annum or so on

#

you're assuming it compounds once per annum

craggy plinth
#

because that's how the information is given here

#

again

craggy plinth
hallow walrus
#

the formula isn't the holy grail

#

think about how you're applying the formula

craggy plinth
#

but how else do we solve

craggy plinth
#

except it has to be a +-?

hallow walrus
#

that formula assumes that the interests compounds annually. do you KNOW that that assumption lies behind that formula?

craggy plinth
#

not sure

#

im guessing yes

hallow walrus
craggy plinth
#

ok

#

we are coming out to the fact that there is an annual interest rate, and we are trying to find it after

hallow walrus
#

and you shouldn't take the negative 4th root here

#

that gives you a ridiculous value for the rate

craggy plinth
hallow walrus
#

the rate of interest can't be -2.07, that means you lose 207% of your money every year

#

i.e you go into debt

craggy plinth
#

exactly

#

so we're thinking

#

that

hallow walrus
#

so we don't take that solution

craggy plinth
#

we are given and before and after numbers

hallow walrus
#

just 1.06....=1+r

craggy plinth
#

9200 before, 12000 after

hallow walrus
#

so r=0.06...

craggy plinth
hallow walrus
#

if it's negative, that is what makes it "go down"

craggy plinth
#

but isn't it exponential decay

#

if the rate is under 1

hallow walrus
#

no, it is exponential decay if the rate is under 0

#

you're confusing two different things

#

(1+r)<1 implies exponential decay yes

#

in other words r<0 is exponential decay

craggy plinth
hallow walrus
#

yeah. and in this case the base is (1+r)...

craggy plinth
#

so the rate

#

can be 0.06?

#

and stay like that fine?

hallow walrus
#

of course it can

#

yes

craggy plinth
#

wait a second

#

oh wait

#

nvm

#

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cold sail
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cold sail
#

i got the answer but

#

i dont understand how differentiating g1 with respect to t finds f_xy

neon crystal
glossy valveBOT
#

Invariance

neon crystal
#

does that help?

cold sail
#

yes but i dont understand why differentiating wrt to y would still find f_xy

#

cz like

#

if you took the partial derivative of f_y wrt to x then u wold get f_xy

#

well i i dont understand the significant of making the x component 0 basically

neon crystal
#

it doesn't matter

cold sail
#

*significance

neon crystal
#

you can set x = 0 before or after differentiation

#

either way you treat it as a constant

#

so it doesn't make a difference

cold sail
#

why tho cz wouldnt setting x = 0 get rid of some y terms too

#

wouldnt that give u an entirely different expression

#

eg the 4x^2y^2

#

in f_x

neon crystal
# cold sail eg the 4x^2y^2

You'd get rid of those anyway. Using that example, if we set (x = 0) first, we get
[\frac{\partial}{\partial y} 4 x^2 y^2 \to \frac{\partial}{\partial y} 4 (0)^2 y^2 = \frac{\partial}{\partial y} 0 = 0]
and if we set (x = 0) after, we get
[\frac{\partial}{\partial y} 4 x^2 y^2 = 8 x^2 y \to 8 (0)^2 y = 0]

#

the order doesn't matter because partial differentiation by y treats x as a constant

#

so if we have a specific constant in mind, it doesn't matter if we set it before or after partial differentiation

#

it would matter if we were differentiating by x, though, for the reasons you state

neon crystal
glossy valveBOT
#

Invariance

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@cold sail Has your question been resolved?

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drifting vapor
#

hi

full forumBOT
drifting vapor
#

i have issues

#

with the formula

#

with y-axis and x-axis

#

on a rotation

#

what the diffrent and whats the formula for both when its about the volume

#

and rotation area?

viral jasper
#

Where are you getting volume?

drifting vapor
#

uhh the figure volume

viral jasper
drifting vapor
#

Let Ω denote the area in the first quadrant between the line y =
16 and the curve y = x^4. When the curve Ω is rotated one revolution around y-
the axis forms a body of rotation. calculate about the volume of the body.

#

like this

viral jasper
#

Ah so early calculus

drifting vapor
#

yea

#

or kinda

#

its mixed

viral jasper
#

There's different formulas based on the axis over which you are rotating

drifting vapor
#

yes i know

#

i want all of them

#

but the rules

#

is typed

#

diffrent

#

online

#

iam confused lol

viral jasper
drifting vapor
#

this is how my preffoser have done

#

and on google

#

it say like only pi

viral jasper
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fallow aurora
#

Can someone please explain to me the Tan, Sin, Cos A and B things? How do I know for future reference how to know which side is the opposite/adjacent?

fallow aurora
#

This is taken directly from yesterdays notes from my class.

fathom saddle
#

A is one of the angles on your triangle. You can see it notated in black ink

#

The "opposite of A" is the side that isn't touching A.

#

The "Adjacent of A" is the side that is touching A, and isn't the hypotenuse

#

The hypotenuse is the longest side of the triangle.

devout valley
#

[in your picture, the red is in reference to the angle at A, and the blue is in reference to the angle at B]

fallow aurora
#

Oh, alright. I was a little confused because in the previous page it was just explaining how to use Sin Cos and Tan, and then it just immediately jumps to this. It felt like a huge jump.

#

Thank you :D

#

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odd rose
#

I have a vector in R4 and I want to find the basis of this vector.

The vector is {[a b c d] | a+b+c+d = 0, a = -c-d}

odd rose
#

So, Ive been having some problems checking on how to find the span of this vector. I did b = -a-c-d and for a = -c-d, i plugged that into [a b c d]. But when i try verifying with other values i get different outputs

full forumBOT
#

Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

odd rose
#

It was a quiz so i cant really show it... i dont have the paper

ember shadow
#

what was the original question though?

balmy lake
#

Looks like a subspace of R4 and asks for a base for the subspace, ig?

odd rose
#

yea

#

how i do it is:
apply the constraints, seperate the variables, factor out the variables, write the span and then check for linear independence

#

But im getting stuck on applying the constraints. Not sure if im doing it right

ember shadow
#

you just row reduce the matrix for those equations

odd rose
#

Yea i know but im stuck on applying the constraints like i said

ember shadow
#

what constraints?

odd rose
#

a+b+c+d = 0, a = -c-d

#

i have to apply those to the vector right?

ember shadow
#

no, you just solve the system of those 2 equations

fathom saddle
#

Those are rules that the vector needs to follow, in order to be a member of the subspace

odd rose
#

yea thats what im doing no?

balmy lake
#

Gnah. Sideways

#

Always

odd rose
#

yea i got the same thing

balmy lake
#

Lemme fix that

ember shadow
#

that's not right

odd rose
#

but then i somehow got 0

balmy lake
#

It is isn't?

odd rose
#

so ik i made a mistake

ember shadow
#

no, b = 0

odd rose
#

-(-c-d)-c-d = 0

balmy lake
#

Oops

#

True that

odd rose
#

so we should have 3 vectors right?

balmy lake
#

No, it's still two vectors

#

Just (-1, 0, 1,0) and (-1,0,0,1) instead of what I wrote

odd rose
#

if we do c = -a-b-d and a = -c-d and then expand and simplify a we get a = a+b

#

so we have 3 variables a,b,d

balmy lake
#

Thanks for catching the miss btw, much appreciated

odd rose
balmy lake
#

Well considering b is 0

#

a=a+b is still true ig

odd rose
#

why is b 0 for this case

balmy lake
#

It is. You cannot find a vector satisfying all constraints with nonzero b

odd rose
#

im just not sure what im doing wrong

balmy lake
#

If you solve the first restraint for b

#

And than plug in the second restraint

#

It will give you b=0

odd rose
#

yes im talking about if we solve the first one for c

balmy lake
#

Well you have to chose 2 of the components as parameters, since with two constraints in R4 the subspace is 2-dimensional

odd rose
#

Can i actually show you how I would do it when solving the first one for c?

balmy lake
#

It doesn't matter which two you chose, as long as it isn't b (because it's zero)

#

Sure

odd rose
#

So c = -a-b-d and a = -c-d

#

Is the correct that the vector now will look like:
[ -c - d
b
c - b
d]

balmy lake
#

Where did you get the c-b from?

odd rose
#

so we had c = -a-b-d

#

and we know a = -c-d

#

so i plugged a into c

balmy lake
#

I see

#

But that immediately gives you b=0

#

Since in c=c-b you can simply subtract c from both sides

odd rose
#

well could i not also just write the augmented matrix of the 3 varibales and solve to see linear independence

balmy lake
#

Sure

odd rose
#

all 3 cols have pivots

#

unless im doing something wrong.. it seems as we have different answers

balmy lake
#

Can you show it?

odd rose
#

sure but it might not make sense. I didnt document it well

balmy lake
#

I'm not sure if I know what you are trying to do here. Where did you get the matrix from?

odd rose
#

You can try solving it your way because it’s the same way you did it when solving for b

balmy lake
#

I can't follow

odd rose
#

Like just try solving it yourself and see what you get

balmy lake
#

I get the exact same thing as above with a different matrix.

odd rose
#

Could you show your work?

balmy lake
#

It'll probably be sideways again, tho... : <

odd rose
#

It’s all good lol

balmy lake
odd rose
#

I’m not sure what ur solving for here

#

could you maybe solve it in this manner

balmy lake
#

Since c and d don't have pivots I can choose them freely.

b does have a pivot and must be 0 since the last line is 1b = 0

a does have pivot, so it isn't free either it is determined in the second to last line by the chosen values for c and d and the calculated value for b:

a+b+c+d=0, where b=0 and c and d are a chosen.

#

Give me a minute

odd rose
#

ok

balmy lake
#

You went from (-c-d, b, c-b, d) as a vector, ig?

odd rose
#

yea

balmy lake
#

I think the problem here is, that b shouldn't exist at this stage anymore

odd rose
#

how tho

balmy lake
#

It's zero.

#

Since the equation c=c-b forces it to be zero

odd rose
#

Ok, im gonna leave this for now tbh

#

Thank you

balmy lake
#

Hm! Sorry : (

odd rose
#

ita ok hah

balmy lake
#

: )

odd rose
#

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royal crest
#

Using Rieman Sum approximate the double integral of x^2 + 4y Da

Where the integral D is region inside the upper unit semi circle centered at the origin (inside the circle, above the x-axis). I want you to approximate this using a polar Riemann sum, dividing theta into 6 sub divisions, and dividing r into 3 subdivisions (so there will be a total of 18 pieces). Use the point with minimum theta and maximum r in each subdivision piece as the point you put into the function.

So far i got:
delta theta: pi/6
delta r: 1/3

lim (m,n goes to infinity) i= 1 sigma m = 6, j= 1 sigma n=3 of F(rj, thetai)

I'm not sure what to do for this part of the question:
"Use the point with minimum theta and maximum r in each subdivision piece as the point you put into the function."

royal crest
#

I'm assuming that I go from pi/6 to 5pi/6
and for r I go from 1/3 to 1 for every pi/6 upto 5pi/6?

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fathom saddle
#

I'd consider drawing the division. It's definitely not easy to keep track

royal crest
#

Hm wdym by drawing the divisions?

#

Suggesting to draw each individual square?

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@royal crest Has your question been resolved?

royal crest
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<@&286206848099549185>

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dusky drift
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can someone tell me why or how this is even wrong?

plain fox
#

can u show working?

quaint prawn
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torn jolt
#

Hii js a quick intro - I've started calculus and I've realised how abysmal my algebra skills are 💀 could you please help 🙏

How in the world do you get

(1/2)x^(-1/2) = 1(2sqrt(x))

woeful nova
#

its 2sqrt(x) or 2/sqrt(x)?

torn jolt
woeful nova
torn jolt
#

I’ll defo be back for more 💀

#

How do I differentiate this

woeful nova
#

give me a second

#

You can do this because there is nothing above in function of x, because otherwise you should use the formula for divisions in the derivatives, I don't know if you understand me because I am using a translator.

#

nothing as a function of x in the numerator,It would also work with constants since you can take them out from the derivatives.

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modern geode
#

.close

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How do I calculate a sin wave?

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warped needle
#

The polynomial P(x) = ax+ 3 satisfies the equation P(P(P(x)))−3P(x) = −2x for all real values
of x, find all polynomials that satisfy this equation.

warped needle
#

not sure if im correct

#

but i got x = -3?

stuck storm
#

the question is not looking for x

warped needle
#

as in P(x) = x-3

#

+*

stuck storm
#

oh ok

#

any value of a would work in this case

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torn jolt
#

im really confused

if the following equation doesnt have an x intercept

torn jolt
#

like clearly it doesnt touch the x line

#

then what did i just calculate

clever sluice
#

in abs only positive value are the outputs

clever sluice
#

absolute value

torn jolt
#

yea...?

clever sluice
#

so how a function that has only positive output values have a negative value?

torn jolt
#

OHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH

torn jolt
clever sluice
#

welcome

torn jolt
#

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stray rock
#

Given is a rectangle ABCD. Let a = AB, b = AD. On the side AB is a point E, on the side AD is a point F and let AE = 2/3a and AF = 1/2b. Where on the line FE should we choose the point G so that the rectangle inscribed in the pentagon DFEBC with the intersection at G and the sides parallel to the sides of the original rectangle, will have the maximum area?

stray rock
#

yeah so I alr took this channel

#

@torn jolt

clever sluice
#

i think its c

stray rock
#

...

ashen crescent
#

Draw a diagram

stray rock
#

yeah I wanted to send but this guy sent his question like its his channel

ashen crescent
#

Looks like he’ll be banned soon anyway

stray rock
#

so like this

#

Im guessing I need to form a function for something and then find the maximum right

#

I thought maybe it has something to do with ratios of the sides

ashen crescent
#

Yeah I believe you need to describe the area of the inner rectangle in terms of a and b

stray rock
#

the answer it "for G we have to choose a point (..., ...)

#

how do we find the point

ashen crescent
#

The BC side of the inner rectangle will be the difference in y component of G and E subtracted from b

#

You can do something similar for the adjacent side

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#

@stray rock Has your question been resolved?

ashen crescent
#

@stray rock are you still stuck?

stray rock
#

I am

#

I had to eat in between also, so thats why I was gone sorry

#

but yeah idk how to do this

ashen crescent
#

Can you do me a favour and redraw the diagram with A and C swapped

stray rock
#

you want me to flip the whole thing?

ashen crescent
#

Yeah

#

In fact, just leave it

stray rock
#

oh

#

alright then

ashen crescent
#

Lets call the area you want to maximise A=L*W

stray rock
#

yep

ashen crescent
#

L is gonna be the horizontal side

#

We can describe L in terms of G and a

#

Since L is just a - Gx

#

Where Gx is the x component of G

#

Right?

stray rock
#

yeah alright I understand

#

and then the same for the width

ashen crescent
#

Yeah, which would be?

stray rock
#

b - Gy

ashen crescent
#

Yeah

#

Now as for G, it lies on the line connecting F and E

#

So we can describe it as (Et, Ft) = (2/3 at, 1/2 bt)

stray rock
#

oh so like multiplied by a factor t

ashen crescent
#

Yes

stray rock
#

alright yeah

ashen crescent
#

then we rewrite A with the new G

stray rock
#

so we replace Gx and Gy with those?

ashen crescent
#

So you have A = (a-2/3at)*(b-1/2bt)

#

Yeah

#

Then, multiply it out and factor ab

stray rock
#

okay wait I have a slight doubt

stray rock
#

so you just described G with those coordinates?

ashen crescent
#

Yeah though, you may be right in spotting something dodgy there

stray rock
#

shouldnt it be

#

oh nvm...

ashen crescent
#

You are right, it is wrong

stray rock
#

well

ashen crescent
#

Give me a second to think about this

stray rock
#

in your case

#

t just has to be <=1 then right

#

for it to work? or is it completely wrong

#

ohhhhh

#

no but is it really wrong?

ashen crescent
#

Yeah, it wouldn’t be lying on the line, it would be a region

stray rock
#

oh yeah true

ashen crescent
#

I think instead it should be G = F(1-t) + E(t), taking a and b as vectors

#

Then when t = 0, G is at F

#

t = 1, G is at E right?

stray rock
#

okay but cant we do it without vectors?

#

if EB is 1/3a

#

and FD is 1/2b

#

that means both of those are being stretched right

#

one is being stretched, and one the opposite

ashen crescent
#

I’m not sure I can see where this is going

stray rock
#

well when G is at F

#

the sides of the rectangle are 1/2b and a

#

when its at E the sides are b and 1/3a

#

maybe something with that? sorry im just kinda bad with vectors

ashen crescent
#

Yeah that is the L and W we had earlier

#

It may be possible to get the equation of the line FE in terms of a and b

#

Under the assumption that A is fixed at the origin

#

Then l_FE would be given by
y = mx + c
y = (1/2b * 3a/2)x + 1/2b

stray rock
#

okay so you got m how

#

ohoh okay

#

sorry

#

yeah I understand

ashen crescent
#

Hang on

stray rock
#

okay wait no just quickly I actually dont understand, how did you get m?

ashen crescent
#

It would be just rise over run -> F/E

#

Then its negative too clearly

stray rock
#

okay

ashen crescent
#

[ y = - \left(\frac b2 \cdot \frac 3{2a}\right)x + \frac b2 ]

glossy valveBOT
ashen crescent
#

It’s a bit hard to describe G with this though

#

Which is why vectors work better i’d say

ashen crescent
#

= 1/2 b - 1/2 bt + 2/3 at

#

Hmm

#

Vectors may make this a bit weird since a and b now have 2 components

stray rock
#

there has to be a way to just do it geometrically

ashen crescent
#

The only problem is describing coordinates of G

stray rock
#

well

#

what about what we did before, with the t right

#

if you stretch 1/b with t

#

if t is 1

#

then you stretch 2/3a with

#

like it has to be something like (a - 2/3a*ct)(b - 1/2t) where c is some number?

#

yk so that then it wont be a region like you said

ashen crescent
#

Where t is in the range 0-1

stray rock
ashen crescent
#

Well what would the coordinates of G be in terms of a, b, c and t then?

stray rock
#

(a - 2/3a*ct, b - 1/2t) this?

#

yk what I mean like if you stretch 1/2b you ahve to stretch 2/3a by the same amount no?

ashen crescent
#

You would stretch by the opposite amount

#

Which is where i got t and 1-t

stray rock
#

so can we use that then?

#

1-t as c

#

or I mean like as

#

a - 2/3a(1-t)

#

and then b - 1/2t?

#

if not then im out of ideas

stray rock
#

yeah so why cant we do that there

stray rock
ashen crescent
#

It changes a bit since length and width are scalars

#

G = b/2(1 - t) + 2/3 at
= 2/3t a + (1-t)/2 b
A = l*w = 2/3t * (1-t)/2 = t - 3t^2

#

This is why I initially said it may be better to flip the diagram, since then A = Gx * Gy

#

A’ = 1 - 6t = 0 iff t = 1/6

#

Then we would get G = 1/6 * 2/3 a + (1-1/6)/2 b

#

= 1/9 a + 5/12 b

#

Possibly

stray rock
#

I have the answer here if you want it

ashen crescent
#

Yeah, go on

stray rock
ashen crescent
#

Can you send the diagram again

stray rock
ashen crescent
#

I need to go get some paper, can’t do this in my head give me a min

#

@stray rock can’t seem to get it and don’t see where i’m going wrong

stray rock
#

it's alright

cinder robin
ashen crescent
#

t would be 1/4

#

And it works

cinder robin
#

oops ok

stray rock
#

really?

ashen crescent
#

Yeah

#

Since G = 2/3ta + ((1-t)/2 )b

#

Then t = 1/4

#

G= (2/3)(1/4)a + (3/4)/2b = 1/6a + 3/8b

#

So A’ = 1-4t

stray rock
#

okay tysmm

ashen crescent
#

A = t - 2t^2 + c

#

If you backtrack a bit and don’t mess up the vectors, you’ll be able to get it

#

Again, I think it would help to flip the diagram

#

Sorry I couldn’t fully help, but hopefully you get the idea

stray rock
#

No dont worry thank you for your time

#

@ashen crescent

#

I appreciate it

#

🙂

#

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honest lark
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honest lark
#

how calculate cos and sin into that form

#

with calculator

lofty vine
#

i dont understand your question

#

how to calculate cos(2pi/3) ?

honest lark
grand hatch
#

Hit the cos button and type in the angle

lofty vine
#

almost all calculators can calculate cos(x) for any x

#

just type it in ur calc

honest lark
#

I use this casio

lofty vine
#

you see that cos button in the middle

honest lark
#

oh

lofty vine
#

also make sure your calc is in radians mode

honest lark