fplot() for three functions

I wonder why my fplot()s output errors instead of the graph below?

Answer 1

[Alan Stevens]

Try using limits, e.g.

fplot(@(t) 16/3*exp(-2*t)-4/3*exp(-8*t), [0 20]);

Also use

t.*exp(...etc)  not  t*exp(...etc)

[Shuqing Qi]

What should we change for the third fplot? There isn't t.*exp but error still exist.

[Alan Stevens]

You need to use

exp(-4*t).*cos(3*t)
and
exp(-4*t).*sin(3*t)

[Shuqing Qi]

That works! Thanks a lot!