You need to create a vector, below you can see a method using the "linspace" function. This creates a vector between 0 and t with 100 elements.
a = 3; % input('Please enter a : ')
b = 2; % input('Please enter b : ')
c = 7; % input('Please enter c : ')
t = 5; % input('Please enter t : ')
% create a vector T between [0 T] with 100 elements
t = linspace(0,t,100);
check = a*b/c;
if check > 1
y = (e^a)*sin(c.*t)./sqrt(b);
elseif check <= 1 && check >= 0
y = sin(a)*sqrt(b.*t)./sin(c);
else % i.e. check < 1
y = cos(a)*e.^(b.*t)./c;
end
figure
plot(t,y)
xlabel('t axis')
ylabel('y values')
grid on
