Math-1
(Odd Semester)
Tutorial Sheet-2
Instructor: Prof. Rajendra K. Ray
1. Show that if lim f (x) exists, then it is unique.
x→x0
2. Consider the function f (x) = 5x + 3 with domain A = R. Show that
lim f (x) = 13
x→2
x+1
3. Consider the function f (x) = with domain A = R. Show that
x2 + 3
1
lim f (x) =
x→1 2
1
4. By using the sequential criterion for continuity, prove that the function f (x) = 7 is not continuous at
x
x=0
5. Find lim f (x) for the following functions:
x→0
(a) f (x) = x + 5
(b) f (x) = |x|
x
; x ̸= 0
(c) f (x) = sgn(x) = |x|
0; x = 0
6. Determine the points of continuity of
1 ; x ̸= 0
f (x) = x
0; x = 0
7. Consider the Dirichlet’s function (
1; x ∈ Q
f (x) =
0; x ∈ R/ Q
Show that f is discontinuous everywhere.
8. Prove that a polynomial function is always continuous on R.
9. Consider the function (
2x2 + 3; x ≤ 3
f (x) =
3x + A; x > 3
find the value of A such that f (x) is continuous at x = 3.
10. Prove that the (six basic) trigonometric functions are continuous on their domain.
11. Find the points of discontinuity for the function f (x) = [x], where [x] denotes the greatest integer
function.
1
12. Let I := [a, b] be a closed bounded interval and let f : I → R be continuous on I. Then prove that f is
bounded on I.
13. Give an example of functions f and g that are both discontinuous at a point c in R such that (a) the sum
f + g is continuous at c, (b) the product f g is continuous at c.
x−2
14. Find the point of discontinuity for the function f (x) = .
x2 + 3x − 10
15. Show that a function f (x) = x2 is continuous but not bounded on [0, ∞).
16. Give an example of a function that is not continuous but bounded on a closed interval.
17. Show that the following function is continuous at x = 0 using the ε − δ definition.
(
x2 Sin(1/x); x ̸= 0
f (x) =
0; x = 0