matlab solve [sig1,sig2] = solve('sig1^2+sig^2 = 920^2','tan(sig2/sig1) = 90*pi/180')解方程组 x^2+y^2=920^2 ; tan(y/x)=90°这个程序是能运行出来的,结果是sig1 =1/atan(1/2*pi)*(-sig2^2+846400*atan(1/2*pi)^2)^(1/2)-1/atan(1/2*pi)*(-sig2

Question

matlab solve
[sig1,sig2] = solve('sig1^2+sig^2 = 920^2','tan(sig2/sig1) = 90*pi/180')
解方程组 x^2+y^2=920^2 ; tan(y/x)=90°
这个程序是能运行出来的,结果是
sig1 =
1/atan(1/2*pi)*(-sig2^2+846400*atan(1/2*pi)^2)^(1/2)
-1/atan(1/2*pi)*(-sig2^2+846400*atan(1/2*pi)^2)^(1/2)
sig2 =
sig2/atan(1/2*pi)
sig2/atan(1/2*pi)
这结果我也看不懂啊,我就像把这结果给转换成数,可用eval语句时就出问题了.
我运行的是
sig1 = eval(sig1)
sig2 = eval(sig2)
给的提示的
Error using ==> sym.mpower at 25
Matrix must be square.
Error in ==> sym.eval at 9
s = evalin('caller',map2mat(char(x)));
Error in ==> Untitled2 at 7
sig1 = eval(sig1)
.
Matrix must be square.

Answer 1

你方程写错了.
'sig1^2+sig^2 = 920^2' 应为 'sig1^2+sig2^2 = 920^2'
>> [sig1,sig2] = solve('sig1^2+sig2^2 = 920^2','tan(sig2/sig1) = 90*pi/180')
sig1 =
920/(1+atan(1/2*pi)^2)^(1/2)
-920/(1+atan(1/2*pi)^2)^(1/2)
sig2 =
920*atan(1/2*pi)/(1+atan(1/2*pi)^2)^(1/2)
-920*atan(1/2*pi)/(1+atan(1/2*pi)^2)^(1/2)