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How to input a rotated vector?

Alan Smith
Posted 11 years ago

New to Mathematica, 10.1, following the guide, but getting wrong results. I'm trying to input a vector after being transformed by a rotation matrix, as:

m1={{a Cos Theta + b Sin Theta},{-a Sin Theta + b Cos Theta}}

but I get a row of 4 numbers as output? I'm trying to get a visualization of this vector so I can compare it with, for example:

m1={{a Cos Theta - b Sin Theta},{a Sin Theta + b Cos Theta}}

and a few other variations. So please give me the exact input I should be typing? Much appreciated, Alan
POSTED BY: Alan Smith
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David Keith
David Keith
Posted 11 years ago
POSTED BY: David Keith
Alan Smith
Alan Smith
Posted 11 years ago

Thanks David, but in 1) I wanted to know how to look at similar matrices to the rotation matrix as well? I tried Clear[y], got the same result. I note that even when I start a new notebook, it seems to keep previous values - is there a clear all that will guarantee nothing left over from previous work? Cheers ALan
POSTED BY: Alan Smith
David Keith
David Keith
Posted 11 years ago
POSTED BY: David Keith
Alan Smith
Alan Smith
Posted 11 years ago
POSTED BY: Alan Smith
David Keith
David Keith
Posted 11 years ago 
In[1]:= r = RotationMatrix[theta]

Out[1]= {{Cos[theta], -Sin[theta]}, {Sin[theta], Cos[theta]}}

In[2]:= r.{x, y}

Out[2]= {x Cos[theta] - y Sin[theta], y Cos[theta] + x Sin[theta]}
POSTED BY: David Keith
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