I am getting error

math error

t=linspace(0,15);

x=(3*t.^2-5)*(t.^3)*sind(t./2)-8*t+27;

v=6*t-2.5*(t.^3)*cosd(t./2)-15*t.^2*sind(t./2)-8;

a=1.25*t^3*sind(t./2)-15*t.^2*cosd(t./2)-30*t*sind(t/2)+6;

plot(t,x,'-',t,v,'--',t,a,'-.','linewidth',1)

title('StreamLine')

xlabel('Time')

ylabel('Velocity')

legend('bestoutside')

grid on

Answer 1

[Star Strider]

Use element-wise operations everywhere and it works —

t=linspace(0,15);
x=(3*t.^2-5).*(t.^3).*sind(t./2)-8*t+27;
v=6*t-2.5*(t.^3).*cosd(t./2)-15.*t.^2.*sind(t./2)-8;
a=1.25*t.^3.*sind(t./2)-15.*t.^2.*cosd(t./2)-30.*t.*sind(t/2)+6;

figure
plot(t,x,'-',t,v,'--',t,a,'-.','linewidth',1)
title('StreamLine')
xlabel('Time')
ylabel('Velocity')
legend('x','v','a', 'Location','bestoutside')
grid on

The legend call also needs to include the plotted variables, and the names appropriate to the values.

.

Answer 2

[Chris]

In addition to dots in front of carets ( .^ ) and slashes ( ./ ), you need dots in front of the asterisks ( .* ) for elementwise multiplication.

Otherwise, Matlab attempts matrix multiplication.

Answer 3

[Stephen23]

You need to use array operations, not matrix operations (you missed this for multiplication):

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

t=linspace(0,15);
x=(3*t.^2-5).*(t.^3).*sind(t./2)-8.*t+27;
%           ^       ^             ^
v=6*t-2.5*(t.^3).*cosd(t./2)-15*t.^2.*sind(t./2)-8;
%               ^                   ^
a=1.25*t.^3.*sind(t./2)-15.*t.^2.*cosd(t./2)-30.*t.*sind(t/2)+6;
%       ^  ^              ^     ^              ^  ^   

plot(t,x,'-',t,v,'--',t,a,'-.','linewidth',1)
title('StreamLine')
xlabel('Time')
ylabel('Velocity')
legend('Location','bestoutside') % I fixed this for you too
grid on