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Type: Posts; User: Ishuda

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1. ## Thread: Matrix equation: Given matrices A, B, use eqn to solve for X, Y

by Ishuda
Replies
7
Views
666

### As I understand it you want to solve the equation...

As I understand it you want to solve the equation
(A B) B-1 \left(\begin{matrix}x\\8\end{matrix}\right)\, =\,
A (B B^{-1}) \left(\begin{matrix}x\\8\end{matrix}\right)\, =\,
A ...
2. ## Thread: Integration: Solve Nm sin2α = ωR * intgrl α:β [(cosβ − cosθ)sinθ cosθ dθ]

by Ishuda
Replies
1
Views
593

\displaystyle \int_\alpha^\beta\, [cos(\beta)\, - cos(\theta)]\, sin(\theta)\, cos(\theta)\,d\theta

. . .\displaystyle =\, cos(\beta)\,\int_\alpha^\beta\, sin(\theta)\,...
3. ## Thread: partial differentials: ∂∂tA(y,t)+6ΛΩ(y2−y)sin(t)=∂2∂y2A(y,t)

by Ishuda
Replies
1
Views
694

### The first place you might start is the separation...

The first place you might start is the separation of variables method, see for example ...
4. ## Thread: Conversion of formula (or equation) given in metric form to US customary unit form

by Ishuda
Replies
6
Views
787

### As Dr.Peterson indicated, using units can...

As Dr.Peterson indicated, using units can sometimes make life easier when transforming from one system of units to another. For example, to convert a distance formula from metric [m=meters] to US...
5. ## Thread: v-Bulletin doesn't like doctors

by Ishuda
Replies
2
Views
984

### If you want exact wording, you can try the [c o d...

If you want exact wording, you can try the [c o d e] [/ c o d e ] tag pair (without the spaces of course)

MD MD

or the \text tag in LaTex
\text{MD MD}

It sounds like you knew all of this...
6. ## Thread: Simplifying Logarithmic Function y=14log2(8x−56)16−12 by applying log properties

by Ishuda
Replies
3
Views
808

### Just what is the equation? y = 14\,...

Just what is the equation?
y = 14\, log_2[(8x-56)*16]\, -\, 12
or what? If that is the equation, what is log(a*b) and 16 = 2?
7. ## Thread: Solving Exact Diff. Eqns w/ Coefficients >1 in Soln: dr/dΘ=(r^2 sin Θ)/(2r cos Θ -1)

by Ishuda
Replies
5
Views
1,277

### The problem is not the incorporation of constants...

The problem is not the incorporation of constants but the integration and the particular assumption of separability. Ignoring this problem for a moment, suppose r = 1/cos(\theta). What is the...
8. ## Thread: Evaluate Accuracy of estimated continuous random variable

by Ishuda
Replies
2
Views
606

### First: "evaluate the accuracy of this estimated...

First: "evaluate the accuracy of this estimated model...". What have you been taught about goodness of fit. What tests can you use? BTW: Only one of those data points fall outside the limits of...
9. ## Thread: Function f such that f (x) = ln (5×-10), for x >2; find range of function & inverse

by Ishuda
Replies
2
Views
887

### (1)When you are given a domain for f(x), the x>2...

(1)When you are given a domain for f(x), the x>2 in your case, you may or may not be able to put in the value of 2. In this case you can't since you would get ln(0) which is undefined. But suppose...
10. ## Thread: Confounding geometric series convergence problem

by Ishuda
Replies
4
Views
631

### Both are correct. They are both representations...

Both are correct. They are both representations of the original function valid in different regions. For example suppose we want the reciprocal 999. Since 999 is (1000-1) we can use your equation...
11. ## Thread: Moment of Inertia Deflection equation

by Ishuda
Replies
3
Views
755

### As I understand it, the question is asking, in...

As I understand it, the question is asking, in part, for units not the particular numerical answer. For example velocity has units of m/s (or equivalent other length units) and time has units of...
12. ## Thread: Parametric Curve: r(t) = [(sin(4t) / sqrt{2}) - 2]i + [2 sqrt{2} cos(4t) + 1]j

by Ishuda
Replies
3
Views
557

### Given the form of an ellipse a (x-x0)^2 + b...

Given the form of an ellipse
a (x-x0)^2 + b (y-y0)^2 - c = 0
where a, b, and c are positive, what is an equivalent a, x, x0, b, y, y0 for your problem. What is the squared modulus of r.
13. ## Thread: Matched Filter for the signal x(t)=t*rect[(t-T/2)/T].

by Ishuda
Replies
1
Views
550

### Sometimes one can resort to tables of transforms...

Sometimes one can resort to tables of transforms to find the answer and work backward
https://en.wikipedia.org/wiki/Fourier_transform#Tables_of_important_Fourier_transforms
14. ## Thread: Matrix Question: How to find sol'n to 4x - 7y + 5z = 13? (Mine ans. is wrong)

by Ishuda
Replies
4
Views
781

### I'm unsure myself. I would expect the question...

I'm unsure myself. I would expect the question to be more like "Solve the equation for x: 4x\, -\, 7y\, +\, 5z\, =\, 13"
in which case the answer is straight forward. Once one writes an equation...
15. ## Thread: Solving set of non-linear implicit eqns: x^3 - 5((y^2)/x) = 6/y & y^3 - 5((x^2)/y) =

by Ishuda
Replies
6
Views
940

### Just as a point reference, these two equations...

Just as a point reference, these two equations are essentially the same formulas. Generally, in a situation such as this I try to manipulate the equation into something 'familiar' So, taking the...
16. ## Thread: Pricing Formula for Selling Price

by Ishuda
Replies
7
Views
1,295

### I do programming (including spreadsheets) for $50... I do programming (including spreadsheets) for$50 an hour and am picky about what I choose to do. So I generally don't give out formulas for programs and spread sheets.

But to try to help a...
17. ## Thread: Pricing Formula for Selling Price

by Ishuda
Replies
7
Views
1,295

### Using final selling price = a * total cost...

Using
final selling price = a * total cost
profit = final selling price - total cost
you should be able to determine what you need

by Ishuda
Replies
2
Views
771

### You might want to look at...

You might want to look at
http://mathworld.wolfram.com/CircularSegment.html
for some ideas. It looks like it might be possible to find out enough to completely describe the circle by combining...
19. ## Thread: Using weightings for dissimilar values

by Ishuda
Replies
6
Views
836

### (1) In order to compare these numbers you should...

(1) In order to compare these numbers you should 'compare apples to apples'. So, after tkhunny, normalize your data first to let us say 'percentages'. Let S be total sales in the rating period, I...
20. ## Thread: plane equation wrong by a minus sometimes

by Ishuda
Replies
9
Views
821

Not quite sure of what you are doing but looks maybe like you have two vectors in a plane so you do the cross product to find the normal...
21. ## Thread: Dividend Payments Per Quarter & Per Year

by Ishuda
Replies
3
Views
791

### Yes, the calculations are correct. For (3)...

Yes, the calculations are correct.

For (3) neither is really more correct, they are the same thing mathematically. Some may prefer one or tuher but it makes no difference.

by Ishuda
Replies
3
Views
544

Wow!
23. ## Thread: Evaluating Polynomial Function

by Ishuda
Replies
3
Views
834

### As a spin off from Bob Brown's post: Two...

As a spin off from Bob Brown's post:
Two things:
(1) Is the original polynomial
f(x) = -x2+5x-2
so that, in reality,
f(x2) = -x4+5x2-2

(2) If that is the original polynomial 'printed in...

by Ishuda
Replies
2
Views
567

### Are you an engineering student? All I can think...

Are you an engineering student? All I can think of is [assuming they really meant the problem as given], sometimes accuracy of measurements are expected to used. Thus if input data is given which...
25. ## Thread: Need help finding maximum of y = -4x^3 - 27x^2 + 5x +45 on -6<=x<=5

by Ishuda
Replies
7
Views
1,342

### Not easily nor without some work, much more than...

Not easily nor without some work, much more than the simple 'take the derivative'. If I really had to do it without derivative, I would, as mmm4444bot said, guess and correct. Before starting that...
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