Javier
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 Sep 25 comment Solving simple modulus with a variable but use inegality operator I don't know if you meant $1$ or $-1$, but in any case $|4x-2| \ge 1$ is equivalent to $4x-2 \le -1$ or $4x-2 \ge 1$. Sep 25 comment Volume of a pyramid as a determinant? @HenningMakholm: Well, it's probably a tetrahedron. Sep 23 comment What is the relevance of the supremum in this question? @dukenukem: Pretty much. Sometimes the supremum is written a little differently, like this: $\displaystyle \sup_{x\in I}|f(x)-g(x)|$. But it's the same thing. Sep 23 comment How do you explain the appearance of a sine in the integral for calculating the surface area of a sphere? @Tpofofn: But where does the $2$, or, if you want, the $\sin \phi$ come from? Sep 22 comment The zero vector If you keep the requirement that addition and scalar multiplication are closed and ask for the subspace to be non-empty, then as a consequence zero must be in it. We just include that axiom to get rid of the empty set. Sep 21 comment Question about solving 2nd order linear differential equations What book are you using, by the way? Sep 21 comment Question about solving 2nd order linear differential equations @Korgan: If it turns out you were right, please tell us, because this is the method I've seen in every differential equations book there is. I'd be very surprised if it was wrong. Sep 20 comment Showing vectors span a vector space by definition This indeed uses only the defintion. I'll edit to make it more explicit. Aug 23 comment A question on Taylor Series and polynomial I think the OP means that the Taylor series is finite. Aug 21 comment Graph $f(x)=\ln x+2$ @AustinBroussard: Yes, that's right. Aug 21 comment Graph $f(x)=\ln x+2$ @AustinBroussard: I don't understand what you said about a horizontal asymptote having to do with $y \to \pm \infty$. A function has a horizontal asymptote, more or less, if it has a limit (not infinity) when $x$ goes to $\pm \infty$, and the logarithm doesn't have one. It simply goes to infinity. Aug 21 comment Graph $f(x)=\ln x+2$ @AustinBroussard: This is a minor terminology thing. Rather than undefined, I would say that there is no y-intercept. The functions $\ln x$ and $\ln x + 2$ are undefined at $x=0$, so there is no y-intercept. Aug 21 comment Graph $f(x)=\ln x+2$ Don't you mean $\ln x + 2$, or maybe $\ln(2+x)$? Aug 13 comment Why can't $\int_0^1\sin(x^2) dx$ be equal to $2$? Forgive me if I'm missing something, but why would it be 2? I mean, with so many numbers to choose from, why would you expect it to be 2? Aug 6 comment Projectile Motion @ladaghini: Nothing, my mistake. Aug 6 comment Projectile Motion @GorillaOne: Yes, sorry, I messed that up. I'll write an answer if I figure it out. Aug 6 comment Projectile Motion @GorillaOne: If you know those, you can find out the time from $x=x_0+v_x t$ Aug 1 comment Derivative of $x^x$ at $x=1$ from first principles @user758556: I guess to use L'Hôpital's you would have to know $\frac{\mathrm{d}}{\mathrm{d}h} (x+h)^h$, which sorts of defeats the purpose of using the limit definition in the first place. Jul 25 comment Having trouble understanding proof of a theorem involving limits of functions and sequences Oh, I get it now. I'm not sure if the argument I'm thinking of is the same one the author is describing, but whatever. Your answer sure helped, though! Jul 25 comment Why are $\sin$ and $\cos$ (and perhaps $\tan$) “more important” than their reciprocals? Fun fact: In some languages, in particular Spanish, sine still has the same not safe for work meaning. This has lead to uncountable repressed giggles in high school math class.