42cos(x) - 28sin(7x + pi/2)


-28?

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70

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D'oh. No, 42 - 28 ... uhhh. *gets out calculator* 14?

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I answered it below.

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Guess I'm not human.

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I got a real easy one...

p(x) = x^2 + 2x + 1
find the real roots of the polynomial

hillarious though!

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I got -3 * (-4) - (-2) = ?

See, I didn't need to take Calculus after all!

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that should be the test to prove you're Asian.

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That's better than a password ;)

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7*6*cos(12pi) - 4*7*sin(14pi + pi/2) = 42-28 = 14

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Quick! Write an evaluator for one of the output formats from this!

It's still loaded with style, but at least it's text.

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The answer is 7 you guys. I just did it in my head.

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I forget calculus syntax. Is that asking you to just evaluate at x=2pi?
In that case, the sin is +1 and the cos is -1 at that point, so it's just 7 - 4 = 3.

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You mean I was only off by 4?! Not bad!

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You have to take the derivative first, then evaluate it at the point x=2pi. Anyway, sin(N*2pi)=0, cos(N*2pi+pi/2)=0.

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I meant "evaluate the derivative", and "the sin is +1" I meant "the derivative at that point is +1". Nikolas did it more thoroughly below.

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He messed up too. :) Must be a lot of programmers hanging around here, and not enough engineers.

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I think you both forgot to apply the chain rule. The derivative of 7Sin[6x] is 42 Cos[6x], etc.

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1. Differentiate
7*cos(6x) + 4*-sin(7x + π/2)

2. Evaluate
7*cos(6*2*π) + 4*-sin(7*2*π + π/2)
those in love with calculators can skip to the last line
= 7*cos(0) + 4*-sin(π/2)
= 7*1 + 4*-1
= 3

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Alternatively, what I did was visualize what the derivatives at those well-known points are: the sin is maximally sloping upwards (+1) and the cos maximally downwards (-1), which got me to your second-to-last step without computing any derivatives directly. :)

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You missed a factor on the derivative. D[ sin(ax) ] = a*cos(ax) . Remember D[ sin(u) ] = cos(u)du . See my solution above.

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zarex has the correct answer above, 14.

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Haha, we suck. Chain rule?

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I'm mostly amused that I probably would have correctly written a program that did it (numeric or symbolic), but I screwed up evaluating it by hand immediately. Anywho, the chain rule is one of the basic few that they teach circa first week of calc.

(When writing a symbolic program I would have double-checked the list by eye and test cases. For the numeric, I'd probably just use a three-point evaluation)

Corrected(?) version:
shose in love with fancy calculators or Mathemtica and it's ilk can just write the answer
1. Differentiate
7*6*cos(x) + 4*7*-sin(x + π/2)

2. Evaluate
7*6*cos(2*π) + 4*7*-sin(2*π + π/2)
those in love with scientific calculators can skip to the last line
= 7*6*cos(2*π) + 4*7*-sin(3π/2)
= 7*6*cos(0) + 4*7*-sin(π/2)
those in love with four-function calculators can skip to the last line
= 7*6*1 + 4*7*-1
= 42 - 28
= 14

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There was a time when I could actually do the math. Now it's like a bad dream. uffff.

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I took 2 years of AP Calc in high school, and now, I hardly remember a lick of it!

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Cincinnati State Tech. a looong time ago :)

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Yeah, yeah, it's funny and all, but wouldn't this be pretty simple for a computer, and pretty damn hard for most humans.

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I think it may have been intentionally constructed to be easy. See my comments above.

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Except for the fact that you have to OCR and parse a math equation correctly.

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so if you know the answer does that mean you're a computer or human? i think humans would get the wrong answer. i know i would.

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Either I'm not a human or I'm totally blonde... -_-"

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i always knew i wasnt a real person...

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cause computers are terrible at math

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very cool )

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So, if you get the correct answer, you must be automated.

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I got the question

-6+7-1=?


so I am human

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so..now I have a lot of variants who I am- martian, animal, machine... but i'm quite sure that i'm not human!

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wtf?

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