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I know how to enter matrices in Wolfram Alpha

{{a,0,0,0},{0,b,0,0},{0,0,c,d},{0,0,e,0}}

I can't seem to multiply this by a column vector

{{a,0,0,0},{0,b,0,0},{0,0,c,d},{0,0,e,0}}{{x/a},{y/b},{p},{q}}

The documentation examples seem to be for matrices with both dimensions >1. How do I input the right-hand part as a column vector?

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1 Answer

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The matrix example page at WolframAlpha has a matrix-vector product example. Basically, you remove the inner sets of curly brackets, and you give it an explicit multiplication symbol, and you get a result:

{{a,0,0,0},{0,b,0,0},{0,0,c,d},{0,0,e,0}}*{x/a,y/b,p,q}

Alternately, you can add a second dummy column to your vector to force WA to think about the matrix the way you want it to, and then ignore the second column of the output.

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