my matlab code is wrong

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Piyanut Nanta 2016-1-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/264981-my-matlab-code-is-wrong

编辑： Walter Roberson 2016-1-24

I'm working on a related to moving objects in a projectile path with external forces from gravity, air resisted and spinning.

Here is my matlab code:

clear all
clc
%Input parameters
h=input('Height in m.(h): ');
%Define assumed parameters 
h1=4.75; %in m.
rt=0.21; %in m.
r=2.00;  %in m.
g=9.81;   %in m/sec^2.
Kd=0.028894; %
m=0.180;  %in Kg. 
%Initial 
theta=atan(2*(h1+rt-h)/r)
theta1=theta*(360/(2*pi))
%หาvoของmodel 1
vm1=sqrt((r*g)/(cos(theta)*sin(theta)))
%หาvoของmodel 2
syms v
V2=vpasolve((-(cos(theta)*sin(theta))/((Kd^2/m^2)*(v^2)*cos(theta)*sin(theta)+g*(Kd/m)*cos(theta)))+((sin(theta)^2*v^2)/(((Kd^2/m^2)*v^4*sin(theta)^2)+(2*g*(Kd/m)*v^2*sin(theta))+(g^2))) == (r/(-(Kd/m)*v^2*cos(theta))), v)
% model 1
tm1=r/(vm1*cos(theta))

Here is the result

Height in m.(h): 0.5
theta =
      1.3502
theta1 =
     77.3624
vm1 =
      9.5867
V2 =
   - 3.2665320034196818433565986779223 + 7.2083367243350947875815002536584i
   - 3.2665320034196818433565986779223 - 7.2083367243350947875815002536584i
                                         7.9139338928729354872162798794152i
                                        -7.9139338928729354872162798794152i
     3.2665320034196818433565986779223 + 7.2083367243350947875815002536584i
     3.2665320034196818433565986779223 - 7.2083367243350947875815002536584i
tm1 =
      0.9536

The result i got seems to be in corect. The results are complex numbers. And the result is not right. I'm wondering if my matlab code is wrong. Or if i can use other comands instead of "vpasolve"