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Grade 12Integral Calculus

check whether both the equations are write
limx(π2tan1x)lnx=0
limx0(cosec x)1lnx=1limx0(cotx)1lnx=e

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4 Years agoGrade 12
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ApprovedApproved Tutor Answer1 Year ago

To determine whether the given limits are correct, we need to analyze each one carefully. Let's break them down one by one, using mathematical principles and properties of limits.

Limit as x Approaches Infinity

First, let's consider the limit:

lim x → ∞ ( π − 2 tan − 1 x ) ln x = 0

As x approaches infinity, the term tan-1(x) approaches π/2. Therefore, we can rewrite the expression:

(π - 2 tan-1(x)) approaches (π - π) = 0.

Now, we have:

lim x → ∞ (0) ln x.

Since ln x approaches infinity as x approaches infinity, we have a form of 0 multiplied by infinity, which is indeterminate. To resolve this, we can rewrite it as:

lim x → ∞ (π - 2 tan-1(x)) ln x = lim x → ∞ ln x / (1 / (π - 2 tan-1(x))).

As x approaches infinity, the denominator approaches 0, and the numerator approaches infinity. This results in an overall limit of 0. Thus, this limit is indeed correct.

Limit as x Approaches Zero

Next, we evaluate:

lim x → 0 (cosec x) ln x = 1

As x approaches 0, cosec x (which is 1/sin x) approaches infinity because sin x approaches 0. The natural logarithm, ln x, approaches negative infinity. This gives us an indeterminate form of infinity times negative infinity.

To analyze this further, we can rewrite it as:

lim x → 0 (cosec x) ln x = lim x → 0 ln x / (sin x).

Using L'Hôpital's Rule, we differentiate the numerator and denominator:

  • Derivative of ln x is 1/x.
  • Derivative of sin x is cos x.

Applying L'Hôpital's Rule gives us:

lim x → 0 (1/x) / (cos x) = lim x → 0 (1 / (x cos x)).

As x approaches 0, this limit approaches infinity, not 1. Therefore, this limit is incorrect.

Final Limit Evaluation

Lastly, we check:

lim x → 0 (cot x) ln x = e

As x approaches 0, cot x (which is cos x/sin x) approaches infinity, while ln x approaches negative infinity, leading to another indeterminate form.

We can rewrite this limit as:

lim x → 0 (cot x) ln x = lim x → 0 ln x / (tan x).

Using L'Hôpital's Rule again:

  • Derivative of ln x is 1/x.
  • Derivative of tan x is sec2(x).

Applying L'Hôpital's Rule gives us:

lim x → 0 (1/x) / (sec2(x)) = lim x → 0 (cos2(x) / x).

As x approaches 0, this limit approaches 0, not e. Therefore, this limit is also incorrect.

Summary of Findings

In summary:

  • The first limit is correct: lim x → ∞ ( π − 2 tan − 1 x ) ln x = 0.
  • The second limit is incorrect: lim x → 0 ( cosec x ) ln x ≠ 1.
  • The third limit is incorrect: lim x → 0 ( cot x ) ln x ≠ e.

Understanding these limits requires a solid grasp of the behavior of functions as they approach critical points, and applying L'Hôpital's Rule can often help resolve indeterminate forms effectively.