# B Graphing an equation by hand

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1. Apr 17, 2017

### mech-eng

I would like to sketch the graph of equation a*b^0.3=constant for a and b are positive real numbers. How do I start?

Which one should be as y-axis, and which one be x-axis. This only affects the shape of the graph. The confusing part for me is that should I use b itself or b^03 as an axis?

Thank you.

2. Apr 17, 2017

### mech-eng

I put b in the horizontal axis and give it values 10, 15, 20, 25, 30, 35, 40, 45 and calculated b^0.3 values. I choose constant=100 and then dividing 100/b^0.3 values I calculate a values. The graph is a curve with negative slope, nonlinear shape but it is like it behaves almost linear between b=20 and b=35 values.

Thank you.

3. Apr 17, 2017

### Staff: Mentor

Here's the graph $ab^{0.3}=a \cdot (b^{0.3})=100$ for control:
http://www.wolframalpha.com/input/?i=a*(b^0.3)=100
It's a hyperbola. The constants $100$ and $0.3$ are only a matter of scaling.

4. Apr 17, 2017

### mech-eng

What is the name/category of this kind of web service? An online calculator?

Thank you

Last edited: Apr 17, 2017
5. Apr 17, 2017

### Staff: Mentor

I don't know, how it is named and by whom. Wolframalpha is a well-known company that provides solutions for simple equations. More detailed solutions and graphics have to be paid by a membership, but for a quick and dirty look-up, they are a good source. Here's another page with similar properties: https://www.desmos.com/calculator

6. Apr 17, 2017

### mech-eng

Are there CAD versions and multiphysics versions of such programs?

Thank you.

7. Apr 17, 2017

### Staff: Mentor

I don't know. Perhaps you could search for them on Google. "free CAD software" of "physics simulations" could be a start.

8. Apr 17, 2017

### Staff: Mentor

9. Apr 18, 2017

### Nidum

In experimental work where you might be needing to determine the actual values for the exponent and the constant from your graph it is often useful to use log axes .

Simple example :

The function y = k . xn then it can be rewritten as log y = log k + n . log x

Plotted on log axes the graph curve now becomes a straight line with n and k being given by the slope and intercept .

10. Apr 18, 2017

### mech-eng

Is this a linearization process? This is very confusing for me because shape of the original and converted one is different so what is same?

Thank you.

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