COMP130_Symbolic

Both symbolic variables and expressions are represented in Matlab using the sym datatype.

• True

• False

Given the following code:

syms x;

expr = x + 2;

x = 10;

What would be the value of expr * 3 ?

• double value 36

• symbolic expression 3*x + 6

• error

• symbolic value 36

Symbolic equations are created using

• =

• ==

• ===

• the isequal function

Which of the following code outputs 2?

• syms x;

  int(diff(x^2))

• syms x;

  diff(diff(x^2))

• syms x;

  diff(int(x))

• syms x;

  int(int(x))

What is the output of the following code?

z = str2sym('a+2*a+(a-1)^2')

collect(z)

• error

• 3*a + (a - 1)^2

• a^2 + a + 1

• a + 2*a + a^2 - 2*a + 1

syms x a b c;

e1 = a*x^2+b*x+c == 0;

Given the above code, which of the following outputs x^2 + 2*x + 3 == 0 ?

• subs(e1,{1, 2, 3})

• subs(e1,[1, 2, 3])

• subs(e1, {a, b, c}, {1, 2, 3})

• subs(e1, (a, b, c), (1, 2, 3))

syms x

y = x^2;

Given the above code, which of the following is most likely to generate the figure?

• fplot(y, [-7,7])

• fplot(y)

• fplot([-7, 7], y)

• plot(x, y)

syms x t z

y = x^2+t-z^3

Given the above code, which of the following outputs 1?

• diff(y, t)

• diff(y)

• diff(y, z)

• diff(y, x)

Which of the following can be used to solve the equation? (Multi-select)

• syms y(t)

  dsolve(diff(y,2)==-y)

• syms y

  solve(diff(y,2)==-y)

• dsolve('D2y=-y')

• solve('D2y=-y')

syms x y

fimplicit(x^2 + (y/2)^2 == 1,[-2,2])

axis equal

Draw the figure generated by the above code.