ITT solve the math problem of the person above you and post a harder problem

The standard order of operations doesn't cover operations of the form a÷b(c), so there's no telling whether to multiply b and c first or to divide a by b first without defining the application of the order of operations in this case.

Pic related is the next harder challenge.

5, see pic related

2+2=

>Find sin(arccos(4/5)) without using a calculator. Show your work.

>Now share your ideas why there's not sufficient information for that answer and I'll show you why there actually is.
cos ur mom is a dumb whore lol

stfu retard the whole point of posting that picture was to derail the thread not get some nerdy sperg to give me the right answer

.6

Guess Veeky Forums doesn't render U+1F41F. That's what 2+2 equals.

I like this one. It took a second thought despite being 7th-grade trig.

By the Pythagorean theorem, the other side is 3, and since sine is the ratio of the opposite side to the hypotenuse, the answer is 3/5.

It seems we need a new problem, so I'll offer one up. Prove a linear functional if continuous if and only if it has bounded norm.

How many suns does it take to roll the moon. A square triangle is so very special mercedes

Circumference of the sun/circumference of the moon
=
2,713,406 miles/6,786
=400

the answer to OP's problem is E, brainlet.

Taking the contrapositive of the statement "if he got all of them right, he got an A" yields "if he didn't get an A, he didn't get all of them right", yielding the answer B, you fucking brainlet

the problem does not specify that he actually has to get all of them right to get an A. it specifies that if he gets all of them right then he gets an A, but it says nothing about if he got only 1 wrong, for example. he could still get an A. I reread it and I can't see a flaw with B, but E is more straight forward and correct.

You're pantsu-on-head retarded mate.

prove that E is wrong?

nice try you sneaky jew

>prove that E is wrong
Where does it imply that you can't get an A without getting all of the multiple choice right?

"gets them all Right" is statement R
"gets an A" is statement A
for clarity's sake, -R is "gets them all wrong"

The teacher says [math]R\implies A[/math]
This is logically equivalent to [math]\neg A\implies \neg R[/math] because it's the contrapositive

(A) is [math] \neg A \implies -R[/math]
this is wrong because A being false implies R is false, not that the opposite of R is true.
(B) is [math]\neg A \implies \neg R[/math]
This is the contrapositive of [math]R\implies A[/math] so it must be true
(C) is [math] \neg R \implies \neg A[/math]
this would only be true if [math]R \iff A[/math] which isn't necessarily true based on [math]R\implies A[/math]. We don't know if [math]A\implies R[/math]
(D) is [math]A \implies R[/math]
this would be true if [math]R\iff A[/math] was true but we don't know that; that's also why (C) is wrong.
(E) is [math]A \implies \neg -R[/math]
This would only be true if [math]\neg -R \implies R[/math], because [math]R \implies A[/math] and this would simplify to [math]A \implies A[/math] which is a tautology (and therefore true). Unfortunately, [math]\neg -R \not\implies R[/math] Because not getting all the answers wrong doesn't imply that you got them all right.

[math]\not\implies[/math] "does not imply" looks like shit but I did the best I could possibly do under the circumstances.

-R is not "gets them all wrong", its "does not get them all right", i.e. "gets one of them wrong at least".

what the fuck is this?
the problem with the proof is that 4 - 9/2 = -1/2. intentionally written 4.5 as 9/2 to make his 2nd line (with the sqrt of the square) less obviously wrong.

Unless there's only one question.

>Where does it imply that you can't get an A without getting all of the multiple choice right?
That's why E is correct. In some tests you can miss a few questions and still get an A. Hence, if he got an A, the ONLY sentence which necessarily follows is he got AT LEAST one right. It's the only response which covers all possible configurations and makes the statements true.

no, that's [math]\neg R[/math]
-R is "gets them all wrong".
I could have just as easily called it W; it's a completely separate statement.

the problem is that 25 is (-5)^2
If you change 25-45+(9/2)^2 to (9/2 -5)^2 everything works out fine.

When you learn to disconnect world parameters from discrete structures, you'll understand why the answer is B.

He could have received an A even if he got all the questions wrong.
All you know is that if he gets all the questions right he gets an A, but that's not necessarily the only way to get an A. And we don't know the minimum number of correct answers guarantees an A. It could be zero.

B is correct. So is E.

Oh sorry, I thought you meant the negation of R by -R.

sqrt(x^2) = abs(x) =/= x in general and in particular if x = -0.5.

Two trains, A and B, are 150km apart and are moving towards each other at 80km/hr, at t=0 a superhero flying at 120km/hr starting at train A begins to fly back and forth between the trains as they approach one another.

What is the total distance the superhero travels by the time the trains collide?

The trains collide after (75/80)*1 hour, so the superhero travels 0.94*120 = 112 km.

E is not correct.

Consider the following scenario: The teacher gives everyone A, regardless of how they answer in the test. In this case you can't deduce that Lewis got at least one question right, since he could get A even if he answered wrong in all the questions.

Let [math] n [/math] be an odd integer [math] >2 [/math] and let [math] f(x)\in \mathbb{Q}[x] [/math] be an irreducible polynomial of degree [math] n [/math] such that the Galois group [math] Gal(f/\mathbb{Q}) [/math] is isomorphic to the dihedral group [math] D_n [/math] of order [math] 2n [/math]. Let [math] \alpha [/math] be a real root of [math] f(x) [/math]. Prove [math] \alpha [/math] can be expressed by real radicals if and only if every prime divisor of [math] n [/math] is a Fermat prime.

you could use that exact same scenario with B.

are you dense? if the teacher gives everyone an A then B can obviously not be true

trivial

Looks like someone needs to Get Rational With These 4 Weird Tricks

dropbox.com/sh/8sf1tvfgg8ujn5j/AABjtx9Za-qFuj60imWns26sa?dl=0&preview=LogicBook-Draft of 7-16-17.pdf

brainlets.

The question doesn't say that the multiple choice section is the only way to get an A. maybe Lewis wrote a killer essay and she gave him a ton of extra credit. maybe Lewis is banging Ms Carroll after class so he gets an A no matter what. who knows. the point is E doesn't follow.

B is objectively correct, and the proof is here Put in concrete terms, Ms Carroll essentially promised that if you got every multiple choice question correct, she'll ignore the rest of the test and just give you an instant A. Thus if Lewis did not get an A, then he did not get the "instant A", which means he did not get all the multiple choice right.

Kek
If the teacher gives everyone an A unconditionally, then "if you didn't get an A, you got at least one question wrong" is still obviously true

t. Josh Dever

lmao brainlet

I know B is correct, but why couldn't it be D as well?

Stupid, dumb, brainlet scum
en.m.wikipedia.org/wiki/Vacuous_truth

If nobody did not get an A, then clearly the set of people who didn't get an A is contained within the set of people who got at least one question wrong, because the former is the empty set

Consider instead of the original question that the superhero travels linearly until the point in time at which the two trains collide. Then the distance that the superhero travels is dependent only on the final tIme t.

We have that the trains move at the same velocity; meaning that they will meet after traveling equal distances. Thus 2v=2x/t implies that t=x/v. Inputting, t=15/16 hours.

Hence the superhero travels a total distance x=120×15/16=30×15/4=450/4 miles=112.5 miles

D doesn't follow necessarily but it may be true, but not necessarily true. Lewis maybe aced all other questions but the multiple choice questions and thus received an A.

Consider a test with 10 questions out of which 5 are multiple choice questions. Acing the other five questions could be enough for Lewis to get an A. So a potential scenario is that Lewis gets an A without getting any if the multiple choice questions right. Hence it doesn't follow necessarily that Lewis got one of the multiple choice questions right.

Ah, I see. I thought the whole exam was multiple choice questions. Tricky.