problem with the symbolic calculation

Dk
2013 11 6
2 个回答
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更新时间：2013 11 6
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Hello! i have a problem: I have a peace of code:
Q1=30;
Q1rad=(pi/180)*Q1;
S1= sym('sin(Q1rad)');
double(S1)
and it doesn.t work because I translate variable to the 'sin(...)' how to make it works? what is the way to calculate expressions with "sin(Q1rad)" and in the end substitute the Q1rad, and calculate the final value of the expression?
best regards! Dmytro.

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 采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-11-6

0 个投票

I translate variable to the 'sin(...)' , what doesthat mean?
If you want double(S1), just write:
sin(Q1rad)

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Dk
Dk 2013-11-6
编辑：Azzi Abdelmalek 2013-11-6
for example, why I can not compute double(C) here?
syms A B C S1 S2 S3;
A=[S1 S2 1;2 3 S2; 3 S1 S3];
B=[S3 S1 1;3 2 S1; 2 S3 S2];
C=A*B;
Q1=30;Q2=20;Q3=10;
Q1rad=(pi/180)*Q1;
Q2rad=(pi/180)*Q2;
Q3rad=(pi/180)*Q3;
S1=sin(Q1rad)
S2=sin(Q2rad)
S3=sin(Q3rad)
double(C)
Azzi Abdelmalek
Azzi Abdelmalek 2013-11-6
%Do not put the cart before the horse
syms A B C S1 S2 S3;
Q1=30;Q2=20;Q3=10;
Q1rad=(pi/180)*Q1;
Q2rad=(pi/180)*Q2;
Q3rad=(pi/180)*Q3;
S1=sin(Q1rad)
S2=sin(Q2rad)
S3=sin(Q3rad)
A=[S1 S2 1;2 3 S2; 3 S1 S3];
B=[S3 S1 1;3 2 S1; 2 S3 S2];
C=A*B;
double(C)
Dk
Dk 2013-11-6
编辑：Azzi Abdelmalek 2013-11-6
:DD sorry maybe my questions are a little stupid, but why I can not compute here double(S1) ? or I should change my approach?
Q1=30;
Q1rad=(pi/180)*Q1;
S1= sym('sin(Q1rad)');
double(S1)
Azzi Abdelmalek
Azzi Abdelmalek 2013-11-6
Q1=30;
Q1rad=(pi/180)*Q1;
S1= sym('sin(Q1rad)')
double(subs(S1))
Dk
Dk 2013-11-6
YES) Thank you!

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更多回答（1 个）

Andrei Bobrov
Andrei Bobrov 2013-11-6

0 个投票

q = [30;20;10];
S = sind(q);
A = [S(1) S(2) 1;2 3 S(2);3 S(1) S(3)];
B=[S(3) S(1) 1;3 2 S(1); 2 S(3) S(2)];
C = A*B;

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