tricky

  1. M

    tricky magic square to solve

    I would like help solving this magic square. I can't find the pattern to it. And the symbols throw me off. The aim is to find the blank square in the bottom right corner. And sorry if this is in the wrong section, Thanks
  2. J

    Help with differentiating a tricky function

    Hello everyone, I am a new user and this is my first post. As a bit of background ... I haven't done much serious maths for about 40 years now. In the early 1970's I studied Astronomy and Physics at Glasgow University and so also had to study university-level Mathematics which was compulsory for...
  3. M

    Tricky tank capacity problem.

    "A tank is supplied by two pipes A and B and emptied by a third pipe C. If the tank is empty and all pipes are opened, the tank can be filled in 20 hours. If the tank is full and A and C are opened, the tank can be emptied in 4 hours. If the tank is full and B and C are opened, the tank can be...
  4. F

    Tricky Percent Growth Problem

    I’ve gota percent growth problem that seems like it should be very basic, but myresults indicate there's something wrong with my methodology (I've attached asummary of the problem). Guidance greatly appreciated!
  5. K

    Tricky trig simplification

    Hi, I have to simplify the following trig expression but I am not sure where to go past a certain point. The expression is: cos[arcsin[4/x]] And the question says To get the correct answer you may need to consider the cases x <= −4 and 4 <= x seperately. I was able to let theta equal...
  6. R

    Tricky Improper Integral

    I was given this integral from a friend $$\int_{0}^{\infty}t^{-\frac{1}{2}}e^{-2014(t+t^{-1})}\,\text{d}t$$ I've noticed that the integrand is undefined on the interval $t = 0$ (as well as negative values) and approaches 0 as $t\rightarrow\infty$ but I have no clue how to begin evaluating the...
  7. C

    tricky calculus problem

    Here's a problem from a calculus book that has me stumped: I don't understand a single thing from the suggestion that the book is giving.. I know how to differentiate, I know how to solve for the equation of a line tangent at a point of a curve using point-slope formula, I know that the line...
  8. M

    Tricky differential

    Hey, I need help with the following total differential In principle, I need to differentiate H wrt q_0, t_{WA_c}, t_{A_cA}, and t_{EC}. The problem are the differentials wrt t_{WA_c} and t_{EC}. I cannot substitute c(s) simply. H \equiv q_0 - \int_{t_{WA_c}}^{t_{A_cA}} \psi(s)...
  9. J

    Tricky geometry problem

    AB and DC are tangents to the small circle. I have proved that AD is parallel to BC. Prove that CD^2-ED^2 = ED x EB
  10. Z

    Tricky Integral

    I'm trying to evaluate the integral: The integral seems to be challenging (computer algebra systems will have a long time dealing this integral). But, the book where I got this integral from came with a hint: What is the value of: in the context of the problem? I'm stuck. How should I...
  11. P

    geometry tricky: 2n dota and 3n lines

    let's have 2n dots and 3n straight line in the plane, with n positive integer. proof that exist at least one point P in the plane such that the sum of the distances of P to the 3n lines is lower that the sum of the distances of P to the 2n points ! I have started with 2 dots two lines, and two...
  12. G

    Need help with this question, very tricky

    The average salary of a male full professor at a public four-year institution offering classes at the doctoral level is $99,685. For a female full professor at the same kind of institution, the salary is $90,330. If the standard deviation for the salaries of both genders is approximately $5200...
  13. S

    trigonometry !! a very tricky trick

    hey there regarding this problem i know that i can use the cosine law and then the sine law to investigate whether the other ange must be 45 or not,, but it takes alot of time and i kinda don't have that much time to solve a problem!! i don't know if am overlooking other way of doing it??
  14. C

    Easy but very tricky geometry problem!

    The image is self explanatory. The problem is really of geometry and not one in the probability area(since the probability matter of the problem is trivial).
  15. S

    tricky question

    Hi can anyone please help to solve the below problem? If 5-3=4 2-8=2 5-1=6 6-3=3 1-7=? please advise as how this is solved methodically Keshav
  16. R

    Tricky induction problem with trig

    Okay, I'm working on a really tricky induction problem where I have to show the following (assuming that \sin{(x/2)}\neq0): \sin{(x)}+2\sin{(2x)}+\ldots +n\sin{(nx)}=\frac{\sin{[(n+1)x]}}{4\sin^2{(x/2)}}-\frac{(n+1)\cos{[(2n+1)(x/2)]}}{2\sin{(x/2)}} for all natural numbers n. I've already...
  17. M

    Geometric series and their application to a tricky question! Help!

    Hi! I'm currently going through my math book in panic trying to soak up information before I go off to college. I want my brain back. So! I had trouble with this simple question. Each year a a sales-person is paid a bonus of 2000 which is banked into the same account which earns a fixed rate...
  18. G

    Tricky Integral(for me)

    I need help integrating this definite integral 0 to pi ∫ (e^cos(x))sin(2x) dx So far I have used a double double angle identity where sin2x=2sin(x)cos(x) I have ∫e^cos(x) * 2sin(x)cos(x) dx I let u=cos(x) du=-sinx dx dx=-du/sinx This turns to - ∫[(e^u) (2u)(sinx)]/sinx du -2∫u(e^u) du...
  19. S

    Tricky Integral

    I'm trying to show that \int_{0}^{\infty}ate^{-at}(1-e^{-at})^{n-2}(1-ne^{-at}) dt = {1 \over {an}} for n \ge 2 I've tried using induction over n, but I'm not sure this is the best way to go. Is there some substitution I'm missing?
  20. V

    Tricky Word Problem

    Hello everyone, Thank you for taking the time to help me. I have never been good at math, and I'm trying to learn now a bit later in life. I've downloaded a free kindle book called CK-12 Algebra 1 - Second Edition. There is a word problem in one of the earlier chapters that is giving me no end...