topic help on using symbolic solve and vectors with units in Mathcad https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2487#M863 <HTML><HEAD></HEAD><BODY><P>Hi,</P><P></P><P>I'm trying to use a the symbolic solve function to rearrange an equation and solve for a variable, but I'm having trouble because the answer is a vector with units. </P><P>Example: given the area of a circle, find the radius. I enter:</P><P></P><P>A:= 3.14 cm^2</P><P>(A = pi * r^2) solve,r-&gt;</P><P></P><P>and it spits out a column vector (displayed here as a row vector)... -&gt; (1cm, -1cm)</P><P>and I want to set that to another variable, say, R1, so I now have: </P><P></P><P>A:= 3.14 cm^2</P><P>R1:= [ (A = pi * r^2) solve,r-&gt; (1cm, -1cm) ]</P><P>R1= (1cm, -1cm) </P><P></P><P>I know it can only be the positive value, so I want to pull that value out:</P><P></P><P>R2:= R1[0 </P><P>this gives me an error: R1 is red and the hover text reads "this value must be an array"</P><P></P><P>How can I set a variable to be the positive radius? (R= 1cm)</P><P>(I know I could just rearrange the equation here for the radius in the first place, but I want to keep it clear where I got the equation from. Also, this is just a simple example and I'd want to do it with something more complicated and want to avoid an algebra mistake)</P><P></P><P>Thank you very much!</P><P></P><P>Eli</P><P>(using Mathcad, version 14.0.0.163 [build 701291152] on windows7, 64bit)</P></BODY></HTML> Thu, 03 May 2018 17:58:11 GMT ptc-4650249 2018-05-03T17:58:11Z help on using symbolic solve and vectors with units https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2487#M863 Hi,I'm trying to use a the symbolic solve function to rearrange an equation and solve for a variable, but I'm having trouble because the answer is a vector with units. Example: given the area of a circle, find the radius. I enter:A:= 3.14 cm^2(A = pi * r^2) solve,r-&gt;and Thu, 03 May 2018 17:58:11 GMT https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2487#M863 ptc-4650249 2018-05-03T17:58:11Z Re: help on using symbolic solve and vectors with units https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2488#M864 <HTML><HEAD></HEAD><BODY><P>There's a couple of approaches</P></BODY></HTML> Mon, 09 Jul 2012 23:42:33 GMT https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2488#M864 RichardJ 2012-07-09T23:42:33Z Re: help on using symbolic solve and vectors with units https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2489#M865 <HTML><HEAD></HEAD><BODY><P>Hi Richard,</P><P></P><P>thank you so much for your response. That is exactly what I was looking for BUT...</P><P></P><P>when I try the same thing you're doing, whether in the same document with different variables or in a new document, I still get an error. This time it's saying that my radius variable is undefined (with both methods). </P><P>I think I must be entering it wrong, although it looks the same as yours (from what I can see).</P><P></P><P>Any thoughts on what I'm doing differently? My file is attached.</P><P></P><P>thanks!</P><P></P><P>Eli</P></BODY></HTML> Tue, 10 Jul 2012 00:58:20 GMT https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2489#M865 ptc-4650249 2012-07-10T00:58:20Z Re: help on using symbolic solve and vectors with units https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2490#M866 <HTML><HEAD></HEAD><BODY><P>It should work. Try downloading and installing the latest available service release for version 14.</P></BODY></HTML> Tue, 10 Jul 2012 12:58:54 GMT https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2490#M866 RichardJ 2012-07-10T12:58:54Z Re: help on using symbolic solve and vectors with units https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2491#M867 <HTML><HEAD></HEAD><BODY><P>Please check the attached Mathcad document below.</P><P></P><P><IMG __jive_id="34608" alt="Pic_1.png" class="jive-image-thumbnail jive-image" src="https://community.ptc.com/legacyfs/online/34608_Pic_1.png" width="450" /></P></BODY></HTML> Wed, 11 Jul 2012 07:43:48 GMT https://www.ptcusercommunity.com/t5/Mathcad/help-on-using-symbolic-solve-and-vectors-with-units/m-p/2491#M867 VladimirN 2012-07-11T07:43:48Z