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lim_x to 0 csc x left(sqrt2cos^2 x + 3cos x - sqrtcos^2 x + sin x + 4right) is equal to :

Solution & Explanation

### Related Formula To evaluate limits of indeterminate types containing radical forms, rationalize the numerator directly by multiplying by its conjugate element matching: (sqrtA - sqrtB)(sqrtA + sqrtB) = A - B ### Core Logic Rewrite the expression as a fraction with sin x in the denominator and rationalize the numerator: lim_x to 0 frac(2cos^2 x + 3cos x) - (cos^2 x + sin x + 4)sin x cdot left(sqrt2cos^2 x + 3cos x + sqrtcos^2 x + sin x + 4right) = lim_x to 0 fraccos^2 x + 3cos x - sin x - 4sin x cdot left(sqrt2cos^2 x + 3cos x + sqrtcos^2 x + sin x + 4right) ### Step 1: Simplify Numerator and Group Terms Express the numerator terms to isolate algebraic patterns: cos^2 x + 3cos x - 4 - sin x = (cos x - 1)(cos x + 4) - sin x Substitute this back into our rationalized limit format: = lim_x to 0 frac(cos x - 1)(cos x + 4) - sin xsin x cdot left(sqrt2cos^2 x + 3cos x + sqrtcos^2 x + sin x + 4right) ### Step 2: Distribute sin x in Denominator Split the limit across the two separated numerator expressions: = lim_x to 0 left[ fraccos x - 1sin x cdot (cos x + 4) - 1 right] cdot frac1sqrt2(1)+3 + sqrt1+0+4 Evaluate the limit component values: lim_x to 0 fraccos x - 1sin x = lim_x to 0 frac-2sin^2(x/2)2sin(x/2)cos(x/2) = lim_x to 0 [-tan(x/2)] = 0 Substituting this zero value simplifies the numerator expression directly: = left[ 0 cdot (1 + 4) - 1 right] cdot frac1sqrt5 + sqrt5 = frac-12sqrt5 ### Pattern Recognition Recognizing that fraccos x - 1sin x to 0 as x to 0 isolates the non-vanishing trigonometric components without needing full multi-stage application of L'Hôpital's rule. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Limits and Derivatives

More Limits, Continuity and Differentiability Previous-Year Questions — Page 2

Q51 2025 Evaluation of Limits
lim_xto 0^+fractanleft(5(x)^frac13right)log_e(1 + 3x^2)left(tan^-13sqrtxright)^2left(e^5(x)^frac43 - 1right) is equal to
  • A. frac115
  • B. 1
  • C. frac13
  • D. frac53

Solution

### Related Formula Standard limits commands: lim_f(x)to 0 fractan(f(x))f(x) = 1 lim_f(x)to 0 fracln(1+f(x))f(x) = 1 lim_f(x)to 0 fractan^-1(f(x))f(x) = 1 lim_f(x)to 0 frace^f(x)-1f(x) = 1 ### Core Logic We can rewrite the limit by grouping each term with its standard balancing factor: lim_xto 0^+ left(fractanleft(5x^1/3right)5x^1/3right) cdot left(frac3sqrtxtan^-13sqrtxright)^2 cdot left(fraclog_e(1 + 3x^2)3x^2right) cdot left(frac5x^4/3e^5x^4/3 - 1right) times frac5x^1/3 cdot 3x^2(3sqrtx)^2 cdot 5x^4/3 ### Step 1: Simplify the Compensating Factor Evaluate the remaining algebraic factor: frac5x^1/3 cdot 3x^29x cdot 5x^4/3 = frac15x^7/345x^7/3 = frac1545 = frac13 Since all individual standard limit terms approach 1, the value of the limit is exactly: 1 cdot 1^2 cdot 1 cdot 1 cdot frac13 = frac13 ### Pattern Recognition Shortcut: For standard limits involving tan(u), ln(1+u), tan^-1(u), and e^u-1 as u to 0, replace each function directly with its argument: frac(5x^1/3)(3x^2)(3sqrtx)^2(5x^4/3) = frac15x^7/345x^7/3 = frac13 ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Limits and Derivatives Class 12 Mathematics: Limits, Continuity and Differentiability
Q71 2025 Points of Discontinuity
The number of points of discontinuity of the function f(x) = left[fracx^22right] - left[sqrtxright], x in [0,4] , where [cdot] denotes the greatest integer function is
Numerical Answer. Answer: 8 to 8

Solution

### Related Formula The greatest integer function [u] changes value and experiences a step discontinuity at any point where its inner argument u takes on an integer value. ### Core Logic Analyze the potential points where either component function argument changes into an integer within the interval x in [0, 4]. 1. For left[fracx^22right]: fracx^22 can range from frac02 = 0 up to frac162 = 8. Integer values are reached at fracx^22 = 0, 1, 2, 3, 4, 5, 6, 7, 8, which means critical test locations are: x = 0, \, sqrt2, \, 2, \, sqrt6, \, sqrt8, \, sqrt10, \, sqrt12, \, sqrt14, \, 4 2. For [sqrtx]: sqrtx can range from sqrt0 = 0 to sqrt4 = 2. Integer values are reached at sqrtx = 0, 1, 2, which means critical test locations are: x = 0, \, 1, \, 4 ### Step 1: Audit Each Critical Point Combine the set of test points within domain boundaries (0, 4): x in \1, \, sqrt2, \, 2, \, sqrt6, \, sqrt8, \, sqrt10, \, sqrt12, \, sqrt14\ Let's evaluate the left and right hand limits at these specific values: - At x = 1: [sqrtx] steps up while left[fracx^22right] is constant implies Discontinuous. - At x = sqrt2: left[fracx^22right] steps up while [sqrtx] is constant implies Discontinuous. - At x = 2: Both functions experience an simultaneous integer step. Let's inspect: - f(2) = [2] - [sqrt2] = 2 - 1 = 1 - f(2^-) = [1.99] - [1.41] = 1 - 1 = 0 Since LHL neq value at point, it is Discontinuous. Continuing this verification down the full combined list confirms that none of the step jumps cancel each other out. ### Step 2: Sum the Discontinuity Points Counting all isolated inner points within (0, 4) yields exactly 8 locations: textTotal Points = 8 ### Pattern Recognition When two greatest integer functions drop steps simultaneously at the same point (like at x=2), always write out the explicit left and right limits manually, as simultaneous steps occasionally step in matching directions and maintain unexpected continuity. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability
Q55 2025 Differentiability of Modulus Functions
Let the function f(x) = (x^2 - 1)|x^2 - ax + 2| + cos |x| be not differentiable at the two points x = alpha = 2 and x = beta. Then the distance of the point (alpha, beta) from the line 12x + 5y + 10 = 0 is equal to:
  • A. 3
  • B. 4
  • C. 2
  • D. 5

Solution

### Core Logic The expression cos|x| is everywhere differentiable. Thus, non-differentiability relies completely on the modulus function containing the quadratic factor, i.e., |x^2 - ax + 2|. Non-differentiability points generally happen where: x^2 - ax + 2 = 0 ### Step 1: Evaluation of Roots Given one of the roots is alpha = 2: 2^2 - a(2) + 2 = 0 implies 6 - 2a = 0 implies a = 3 Substituting a=3 gives the other root beta = 1. However, evaluating differentiability at x=1 reveals properties that invalidate standard options. ### Step 2: Conclusion Due to a technical contradiction in the configuration of the differentiable constraints at x=1, this question was officially dropped by NTA. ### Pattern Recognition If a quadratic inside a modulus has distinct real roots, it normally creates non-differentiable sharp turns unless a repeated multiplying factor outside cancels it out. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability
Q74 2025 Continuity and Differentiability of Piecewise Functions
Let f(x) = begincases 3x, & x < 0 \\ min left\1 + x + [ x ], x + 2 [ x ] right\, & 0 le x le 2 \\ 5, & x > 2 endcases where [.] denotes greatest integer function. If alpha and beta are the number of points, where f is not continuous and is not differentiable, respectively, then alpha + beta equals....
Numerical Answer. Answer: 5 to 5

Solution

### Related Formula A function is discontinuous if left-hand and right-hand limits mismatch at boundary transitions. Non-differentiability occurs at discontinuities or sharp turns. ### Core Logic Simplify the greatest integer component [x] by expanding over integer intervals:
Continuity and Differentiability of Piecewise Functions diagram for Q74 - JEE Main 2025 Morning
Continuity and Differentiability of Piecewise Functions diagram for Q74 - JEE Main 2025 Morning
f(x) = begincases 3x, & x < 0 \\ x, & 0 le x < 1 \\ x + 2, & 1 le x < 2 \\ 5, & x > 2 endcases ### Step 1: Testing Continuity Limits Check continuity at structural boundaries: At x = 0: textLHM = 0, textRHM = 0 implies Continuous. At x = 1: textLHM = 1, textRHM = 3 implies Discontinuous. At x = 2: textLHM = 4, textRHM = 5 implies Discontinuous. Thus, alpha = 2 points of discontinuity (x in \1, 2\). ### Step 2: Testing Differentiability Parameters Discontinuities automatically introduce non-differentiability. Now check smooth corners at the remaining continuous transition x = 0: f^prime(0^-) = 3, quad f^prime(0^+) = 1 implies textNot differentiable at x=0. Thus, beta = 3 points of non-differentiability (x in \0, 1, 2\). alpha + beta = 2 + 3 = 5 ### Pattern Recognition Discontinuities automatically break differentiability. Always count them first before checking derivatives at smooth corner points. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Limits, Continuity and Differentiability
Q69 2025 Continuity of Piecewise Functions
Let f(x) = begincases (1 + ax)^1/x & , x < 0 \\ 1 + b & , x = 0 \\ frac(x + 4)^1/2 - 2(x + c)^1/3 - 2 & , x > 0 endcases [cite: 680] be continuous at x = 0[cite: 681]. Then mathrme^mathrmacdot b cdot c is equal to[cite: 681]:
  • A. 64
  • B. 72
  • C. 48
  • D. 36

Solution

### Related Formula Continuity definition condition frame: lim_x rightarrow 0^- f(x) = f(0) = lim_x rightarrow 0^+ f(x) ### Core Logic Evaluate Left-Hand Limit (LHL) using standard forms [cite: 1410]: textLHL = lim_x rightarrow 0^- (1+ax)^1/x = e^a [cite: 1410] Given baseline definition states f(0) = 1+b [cite: 1410]. For Right-Hand Limit (RHL) to be finite and valid, the numerator tracking towards 0 means the denominator must also balance towards 0 to avoid divergence [cite: 1411]: lim_x rightarrow 0^+ left[(x+c)^1/3 - 2right] = 0 implies c^1/3 = 2 implies c = 8 [cite: 1414] ### Step 1: Applying L'Hopital's rule to the RHL With c=8, evaluate RHL limit expressions using derivatives [cite: 1411]: textRHL = lim_x rightarrow 0^+ fracfrac12sqrtx+4frac13(x+8)^-2/3 = fracfrac12(2)frac13(8)^-2/3 = fracfrac14frac13 cdot 4 = frac14 cdot 12 = 3 [cite: 1411, 1415] ### Step 2: Equating limits for parameter solutions Equate continuous criteria milestones together [cite: 1416]: e^a = 1 + b = 3 [cite: 1416] e^a = 3 implies b = 2 [cite: 1416] Compute the ultimate target combination product configuration [cite: 1416]: e^a cdot b cdot c = 3 cdot 2 cdot 8 = 48 [cite: 1416] ### Pattern Recognition Determining missing root constants inside indeterminate fraction structures handles calculations swiftly before running formal limits. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability

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