- #1

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**QUESTION:**

Plot the function f(x) = cosx sin(2x) and its derivative, both on the same

plot, for π ≤ x ≤ π . Plot the function with a solid line, and the derivative with

a dashed line. Add a legend and label the axes.

**Okay, so this is what I have so far in a script file...**

x = [-pi: 0.01: pi];

y = cos(x)*sin(2*x);

yd = 2*cos(x)*cos(2*x)-sin(x)*sin(2*x);

plot (x,y,x,yd)

**But then I get this error:**

??? Error using ==> mtimes

Inner matrix dimensions must agree.

Error in ==> p11 at 3

y = cos(x)*sin(2*x);

I'm not worried about the details, that should be easy enough. (dotted/solid lines and legends and axes labeling.) I just want to make sure I can get it to plot. Also it asks to plot for π ≤ x ≤ π, but i have a feeling it means -π ≤ x ≤ π.

It looks pretty simple, but I'm still learning this program and it's proving to be more difficult than it should be. Anyone have any ideas what's wrong with my script?

Thanks!