Advertisements
Advertisements
Question
Discuss the continuity of the cosine, cosecant, secant and cotangent functions.
Advertisements
Solution
(i) f(x) = cos (x)
Let c be any real number.
If f(x) is continuous at x = c, this implies:
f(c) = `lim_(x -> c^+)` f(x) = `lim_(x -> c^-)` f(x)
⇒ (cos c) = (cos c) = (cos c)
This statement is true; that is, f(x) is continuous at every point on the real number line.
(ii) f(x) = cosec (x)
Let c be any real number.
If f(x) is continuous at x = c, this implies:
f(c) = `lim_(x ->^+)` f(x) = `lim_(x -> c^-)` f(x)
⇒ (cosec c) = (cosec c) = (cosec c)
This statement is true; that is, f(x) is continuous at every point on the real number line.
(iii) f(x) = sec (x)
Let c be any real number.
If f(x) is continuous at x = c, this implies:
f(c) = `lim_(x -> c^+)` f(x) = `lim_(x -> c^-)` f(x)
⇒ (sec c) = (sec c) = (sec c)
This statement is true; that is, f(x) is continuous at every point on the real number line.
(iv) f(x) = cot (x)
Let c be any real number such that (n − 1)π < x < nπ, where n represents an integer point.
If f(x) is continuous at x = c, this implies:
f(c) = `lim_(x -> c^+)` f(x) = `lim_(x -> c^-)` f(x)
⇒ (cot c) = (cot c) = (cot c)
This statement is true; that is, f(x) is continuous at every point on the real number line between (n − 1)π and nπ.
Now if we consider c such that c = nπ, where n represents an integer point, then:
If f(x) is continuous at x = c, this implies:
f(c) = `lim_(x -> c^+)` f(x) = `lim_(x -> c^-)` f(x)
⇒ ±∞ = ±∞ = ±∞
That is, f(x) is continuous at every point on the real number line except at the nπ-type points.
APPEARS IN
RELATED QUESTIONS
If f (x) is continuous on [–4, 2] defined as
f (x) = 6b – 3ax, for -4 ≤ x < –2
= 4x + 1, for –2 ≤ x ≤ 2
Show that a + b =`-7/6`
Find the value of k so that the function f is continuous at the indicated point.
f(x) = `{(kx^2", if" x<= 2),(3", if" x > 2):}` at x = 2
Find the value of k so that the function f is continuous at the indicated point.
f(x) = `{(kx +1", if" x<= pi),(cos x", if" x > pi):}` at x = π
Let \[f\left( x \right) = \frac{\log\left( 1 + \frac{x}{a} \right) - \log\left( 1 - \frac{x}{b} \right)}{x}\] x ≠ 0. Find the value of f at x = 0 so that f becomes continuous at x = 0.
Prove that the function \[f\left( x \right) = \begin{cases}\frac{\sin x}{x}, & x < 0 \\ x + 1, & x \geq 0\end{cases}\] is everywhere continuous.
The function \[f\left( x \right) = \begin{cases}x^2 /a , & \text{ if } 0 \leq x < 1 \\ a , & \text{ if } 1 \leq x < \sqrt{2} \\ \frac{2 b^2 - 4b}{x^2}, & \text{ if } \sqrt{2} \leq x < \infty\end{cases}\] is continuous on (0, ∞), then find the most suitable values of a and b.
Discuss the continuity of the following functions:
(i) f(x) = sin x + cos x
(ii) f(x) = sin x − cos x
(iii) f(x) = sin x cos x
Show that f (x) = | cos x | is a continuous function.
What happens to a function f (x) at x = a, if
If the function \[f\left( x \right) = \frac{\sin 10x}{x}, x \neq 0\] is continuous at x = 0, find f (0).
Determine the value of the constant 'k' so that function f
\[f\left( x \right) = \begin{cases}\frac{\left| x^2 - x \right|}{x^2 - x}, & x \neq 0, 1 \\ 1 , & x = 0 \\ - 1 , & x = 1\end{cases}\] then f (x) is continuous for all
If \[f\left( x \right) = \begin{cases}\frac{1 - \sin x}{\left( \pi - 2x \right)^2} . \frac{\log \sin x}{\log\left( 1 + \pi^2 - 4\pi x + 4 x^2 \right)}, & x \neq \frac{\pi}{2} \\ k , & x = \frac{\pi}{2}\end{cases}\]is continuous at x = π/2, then k =
Let \[f\left( x \right) = \left\{ \begin{array}\\ \frac{x - 4}{\left| x - 4 \right|} + a, & x < 4 \\ a + b , & x = 4 \\ \frac{x - 4}{\left| x - 4 \right|} + b, & x > 4\end{array} . \right.\]Then, f (x) is continuous at x = 4 when
The function
If \[f\left( x \right) = \frac{1 - \sin x}{\left( \pi - 2x \right)^2},\] when x ≠ π/2 and f (π/2) = λ, then f (x) will be continuous function at x= π/2, where λ =
The value of a for which the function \[f\left( x \right) = \begin{cases}\frac{\left( 4^x - 1 \right)^3}{\sin\left( x/a \right) \log \left\{ \left( 1 + x^2 /3 \right) \right\}}, & x \neq 0 \\ 12 \left( \log 4 \right)^3 , & x = 0\end{cases}\]may be continuous at x = 0 is
If \[f\left( x \right) = x \sin\frac{1}{x}, x \neq 0,\]then the value of the function at x = 0, so that the function is continuous at x = 0, is
The value of a for which the function \[f\left( x \right) = \begin{cases}5x - 4 , & \text{ if } 0 < x \leq 1 \\ 4 x^2 + 3ax, & \text{ if } 1 < x < 2\end{cases}\] is continuous at every point of its domain, is
Find the values of a and b so that the function
Find the values of a and b, if the function f defined by
If \[f \left( x \right) = \sqrt{x^2 + 9}\] , write the value of
The function f (x) = |cos x| is
The function f (x) = 1 + |cos x| is
If f(x) = 2x and g(x) = `x^2/2 + 1`, then which of the following can be a discontinuous function ______.
`lim_("x" -> 0) (1 - "cos" 4 "x")/"x"^2` is equal to ____________.
If `f`: R → {0, 1} is a continuous surjection map then `f^(-1) (0) ∩ f^(-1) (1)` is:
For what value of `k` the following function is continuous at the indicated point
`f(x) = {{:(kx^2",", if x ≤ 2),(3",", if x > 2):}` at x = 2
For what value of `k` the following function is continuous at the indicated point
`f(x) = {{:(kx + 1",", if x ≤ pi),(cos x",", if x > pi):}` at = `pi`
Find the values of `a` and ` b` such that the function by:
`f(x) = {{:(5",", if x ≤ 2),(ax + b",", if 2 < x < 10),(21",", if x ≥ 10):}`
is a continuous function.
Which concept is fundamental in determining continuity of a function at a point?
For \[f(x)=\frac{p(x)}{q(x)}\], where \[p(x)\] and \[q(x)\] are polynomial functions, where is \[f\] continuous?
Which statement about \[\sin x\] and \[\cos x\] is correct?
Let \[g(x)=\sin x\] and \[h(x)=x^2\]. Which expression equals \[(g\circ h)(x)\]?
