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MathsMediumClass 12

Properties of Definite Integrals — All 9 properties

Definite Integration & Area

17

JEE Qs

8%

Hard

75

min

Master the King Property (P3/P4) and symmetry properties (P6/P7); they are the most common tools for simplifying definite integrals in JEE problems.

🧮 Key Formulas

P0: ∫[a,b] f(x) dx = ∫[a,b] f(t) dt
P1: ∫[a,b] f(x) dx = -∫[b,a] f(x) dx
P2: ∫[a,b] f(x) dx = ∫[a,c] f(x) dx + ∫[c,b] f(x) dx
P3 (King Property): ∫[a,b] f(x) dx = ∫[a,b] f(a+b-x) dx
P4 (Queen Property): ∫[0,a] f(x) dx = ∫[0,a] f(a-x) dx
P5: ∫[0,2a] f(x) dx = ∫[0,a] f(x) dx + ∫[0,a] f(2a-x) dx
P6: ∫[0,2a] f(x) dx = 2∫[0,a] f(x) dx if f(2a-x) = f(x)
P6: ∫[0,2a] f(x) dx = 0 if f(2a-x) = -f(x)
P7: ∫[-a,a] f(x) dx = 2∫[0,a] f(x) dx if f(x) is even (f(-x) = f(x))
P7: ∫[-a,a] f(x) dx = 0 if f(x) is odd (f(-x) = -f(x))
P8 (Periodicity): ∫[0,nT] f(x) dx = n * ∫[0,T] f(x) dx if f(x) is periodic with period T
P8 (Periodicity): ∫[a, a+T] f(x) dx = ∫[0, T] f(x) dx if f(x) is periodic with period T

✅ Key Points for JEE

  • 1The King Property (P3/P4) is arguably the most powerful and frequently used property, often simplifying complex integrands involving trigonometric functions or logarithms.
  • 2Always check for symmetry (even/odd functions) when limits are of the form [-a, a] or [0, 2a] as this can immediately reduce the integral to zero or simplify calculations significantly.
  • 3When facing piecewise functions or integrals with absolute values, use property P2 (splitting limits) at critical points to break down the integral into manageable parts.
  • 4For periodic functions, the value of the definite integral over any interval whose length is an integral multiple of the period can be simplified using P8.
  • 5Sometimes, combining two properties (e.g., P3 and then P7/P6) is required to solve an integral, or applying a property (like P3) and adding the original and new integral is key to evaluation.

⚠️ Common Mistakes

  • Incorrectly identifying even/odd functions or f(2a-x) = f(x)/-f(x), leading to wrong application of P6/P7.
  • Failing to recognize when to apply the King Property (P3/P4), especially when the integrand looks complex but simplifies drastically upon application.
  • Errors in splitting limits (P2) for absolute value or greatest integer functions, often missing all critical points or sign changes.
  • Not checking for periodicity when appropriate, particularly for trigonometric functions, which can simplify limits of integration significantly.

NCERT Chapters

  • Class 12 Mathematics Ch 7: Integrals