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2015-11-03 07:53:23 -0600 asked a question Graphing 3 planes

Disclaimer: I'm new to linear algebra and an intermediate with Sage.

How can I graph the following planes? This example is taken from Linear Algebra and Its Applications by Strang. I've tried to follow these instructions, but I'm stuck. Thanks!

image description

2015-09-24 10:49:42 -0600 commented answer Graph or plot a system of inequalities

This is a clever solution. I didn't know you could use the solver with rhs and plot to graph relations. The problem is that it doesn't shade the inequality's region like region_plot does.

2015-09-24 10:47:48 -0600 commented answer Graph or plot a system of inequalities

You beat me to it. I was going to suggest:

var("x y")

f1 = x >= y^2 + 2*y -3
f2 = y >= x-3
f3 = x == y^2 + 2*y -3
f4 = y == x-3

rx = (-10,15)
ry = rx

i = [f1, f2] # i meaning inequalities

p = region_plot(i, rx, ry)
p+= implicit_plot(f3, rx, ry, color="black")
p+= implicit_plot(f4, rx, ry, color="black")

show(p, axes="true", frame=False, aspect_ratio=1)
2015-09-24 07:34:10 -0600 asked a question Graph or plot a system of inequalities

Disclaimer: I'm somewhat new to Sage.

Is it possible to graph a system of inequalities in Sage? I'd like to reproduce the following system (top of image) and its graph (bottom of image). Based on (http://www.sagemath.org/tour-graphics...), it seems like I need a region plot, but I'm not sure.

image description

2015-08-05 18:57:59 -0600 asked a question How to plot a parabola (conic): y²=4ax

I'm learning about conics, specifically parabolas, and I'd like to plot them. I already know how to do plot(x^2)), but what about y²=4ax ? I understand that representation is a relation, not a function, so that probably eliminates plot(f(x)). But, I'm stuck on how I might plot that so-called "general form" of a parabola.

Thanks!

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2015-07-20 09:02:25 -0600 commented answer Label each point

very nice! thank you!

2015-07-19 01:04:48 -0600 asked a question Label each point

Is it possible in Sage to label each point in a 2-D plot? I'd like to create something like this: image description

2015-07-13 11:04:20 -0600 commented answer Plots: display period information

Perfect! It didn't occur to me to use a list comprehension.

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2015-07-10 16:25:41 -0600 asked a question sin arguments not distributed?

In both Wolfram Alpha and Google, I can type the following:

3sin(2(x-(pi/4)))+1

and those systems see

3sin(2(x-(π/4)))+1  (e.g., 2 is distributed to x and π/4)

but when I enter it into Sage Math, it's show(f(x)) indicates

3sin(-1/2π+2x)+1

as shown here: http://picpaste.com/1-3llQDTs0.png (sorry, I can't upload images on ask.sagemath.org since I have less than 60 points)

which obviously differs from Wolfram Alpha and Google. What am I doing wrong?

Thanks!

2015-07-10 15:32:46 -0600 asked a question Plots: display period information

Disclaimer: I'm new to Sage.

Is it possible to indicate the period when plotting periodic functions?

According to my trig book, for example, "you have a graph that has four complete cycles of the sine curve in the space where you would usually find one", as shown here:

f(x)=-2*sin(4*(x+pi/4))+3
plot(f(x),(x,-2*pi,2*pi))

Is there a way to indicate each period? If not, could I approximate it with ticks? Something like:

f(x)=-2*sin(4*(x+pi/4))
P=points([(pi,0),(2*pi,0)], pointsize=40, color='red')
P+plot(f(x),(x,-2*pi,2*pi), ticks=pi/2, tick_formatter=pi)
2015-07-10 14:14:28 -0600 commented answer Beginner: Plot sin 2x or 4cos 2x

Perfect! Thank you for the detail. I was trying sin(2x) not sin(2*x) and getting an error.

2015-07-10 14:13:17 -0600 commented answer Beginner: Plot sin 2x or 4cos 2x

excellent! thank you!

2015-07-10 14:12:58 -0600 marked best answer Beginner: Plot sin 2x or 4cos 2x

Disclaimer: I'm a beginner with Sage.

I'm working with transformations and translations of trig functions, and although I can "plot(sin, (-2,2))" without trouble, how do I plot the following?

sin 2x

or

4cos 2x

or

3sin (x+5) -3

Thanks!