MATLAB: How to write a mathematical function in MATLAB

differentiation

Hi All,

I want to write velocity vector in terms of its component in x, y and z direction , say V= V(t)_x i^+V(t)_y j^+V(t)_z k^. These components are functions of time.

Then I want to differentiate that function with respect to time.

How to do that ?

Any suggestion will be appreciated!

Thanks in advance.

Best Answer

%if true
  % code
% end
syms t i j k
vx = t^2;
vy = t^3;
vz = t^4;
V = @(t) vx*i+vy*j+vz*k;
VV = diff(V,t);% differentiate

Use symbolic expressions and diff function

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MATLAB: Replace expression of variables with an equivalent variable

Your substitution can't work because you defined "theta_v" to be "omega*t + phi_v". So you're just substituting "omega*t + phi_v" for the same thing. If you want to keep "theta_v" then don't define it as "omega*t + phi_v". Keep it as a symbolic function, and substitute in at the end.

>> syms x
>> syms theta_v(t)
>> syms Vx
>> v = Vx*sin(theta_v)
v(t) =
Vx*sin(theta_v(t))
>> y = diff(v, t)
y(t) =
Vx*cos(theta_v(t))*diff(theta_v(t), t)
>> syms omega phi_v
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ans(t) =
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MATLAB: Cross product of two vectors(function)

V1=[v1x,v1y,v1z];
V2=[v2x,v2y,v2z];

Wrong code! you already have V1 and V2 not the other variables.

v1x=V1(1);v1y=V1(2);v1z=V1(3)
v2x=V2(1);v2y=V2(2);v2z=V2(3)

or just forget about those new variables and use only the V1 and V2

function [result]=cross_product(V1,V2)
%CROSS_PRODUCT calculates the cross product of two vectors.
i=(V1(2)*V2(3) - V2(2)*V1(3));
j=(V1(3)*V2(1) - V2(3)*V1(1));
k=(V1(1)*V2(2) - V2(1)*V1(2));
%result=i+j+k; %this is wrong
result=[i,j,k]; %this is right
end

Best Answer

Related Solutions

MATLAB: Replace expression of variables with an equivalent variable

MATLAB: Cross product of two vectors(function)

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