Question

MATLAB难题：如何把一个复杂的含符号表达式按按一定精度化简.

Answer 1

digits(3)

>> vpa(y)

ans =

.473e-15*(.507e31-.448e31*z1^2/(((z1-.950+x-1.*(.783-.824*x)/(.950-1.*x)/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*cos((4.06-2.75*x)/z1)+((.950-1.*x)^2/(2.61-2.75*x)+.300/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*(4.06-2.75*x)/z1)^2+((z1-.950+x-1.*(.783-.824*x)/(.950-1.*x)/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*sin((4.06-2.75*x)/z1)-1.*((.950-1.*x)^2/(2.61-2.75*x)+.300/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*cos((4.06-2.75*x)/z1))^2))^(1/2)/z1*(((z1-.950+x-1.*(.783-.824*x)/(.950-1.*x)/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*cos((4.06-2.75*x)/z1)+((.950-1.*x)^2/(2.61-2.75*x)+.300/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*(4.06-2.75*x)/z1)^2+((z1-.950+x-1.*(.783-.824*x)/(.950-1.*x)/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*sin((4.06-2.75*x)/z1)-1.*((.950-1.*x)^2/(2.61-2.75*x)+.300/(1.+(2.61-2.75*x)^2/(.950-1.*x)^2)^(1/2))*cos((4.06-2.75*x)/z1))^2)^(1/2)-.364+z2/z1*(tan(.940*z2/(z2+2.-2.*x))-.364)