Trouble plottiing a trig function

I want to plot the function sin^3(x)/((1-cos(x))^5) for values of x=[:pi].

So first I declared x = [0:.01:pi]

Then I try creating y.

When I set y = sin(x).^3 I do get a continous plot.

But when I start really tring to build the function for y, where y = sin^3(x)/((1-cos(x)).^5) i just get one single value when I do

plot(x,y).

Why is it all of a sudden giving me single value when I suddenl introduce the denominator?

Answer 1

[John D'Errico]

Ok. You knew you had to use the .^ operator to raise the elements to a power, element-wise. There are also .* and ./ operators, for the same reason. Use them.

And then, we see you still did not even take your own advice, even though you said you knew how to raise sin(x) to a power. You still wrote the wrong expression.

y = sin(x).^3./((1-cos(x)).^5)
          __ _

Note the two differences in what I wrote.

You should also learn to use linspace, NOT the colon operator for this. Why?

x = [0:.01:pi];

Look at the final element of x. Is it pi? No. In fact, it is wrong by a fair amount, that in some problems will be significant.

pi - x(end)
ans =
0.00159265358979299

However, if you do this:

x = linspace(0,pi,100);
pi - x(end)
ans =
0

Now it hits the endpoint exactly.

[Snow]

The fact i did not know ./ was operator tells me I need to go back to the basics. Its been a long time since I've used matlab. Thank you for your help.

[John D'Errico]

Then don't forget also the .* operator. No need to worry about addition and subtraction though. No dots there.

[Image Analyst]

@Anthony Ramirez If John's advice worked, please click the "Accept this answer" link to award John "reputation points". Thanks in advance. 🙂