Solution
Related Formula
Greatest Integer Function boundaries:
[f(x)] = k for k ≤ f(x) < k+1, k in ZCore Logic
Analyze the value variations of f(x) = e1-x across the integration limits [0, e³] to break down the integral into distinct piecewise continuous intervals.
Step 1: Determine Step Function Transition Points
Let y = e1-x.
- At x = 0 y = e¹ ≈ 2.718
- As x increases, e1-x decreases monotonically.
- Find x where y = 2 e1-x = 2 1-x = ln 2 x = 1 - ln 2.
- Find x where y = 1 e1-x = 1 1-x = 0 x = 1.
- At the final boundary x = e³ y = e1-e³, which is a very small positive decimal strictly inside (0,1).
Step 2: Split the Definite Integral
Rewrite the integral based on the isolated interval blocks:
I = ∫₀1-ln 2 2 dx + ∫1-ln 2¹ 1 dx + ∫₁e³ 0 dxStep 3: Perform Integrations
I = 2[x]₀1-ln 2 + 1[x]1-ln 2¹ + 0 I = 2(1 - ln 2 - 0) + 1(1 - (1 - ln 2)) = 2 - 2ln 2 + ln 2 = 2 - ln 2Step 4: Solve for Alpha Cubed
Compare the integrated value to α - ln 2:
α - ln 2 = 2 - ln 2 α = 2 α³ = 2³ = 8Pattern Recognition
Always map the function values at the extreme boundary points first. Tracking the downward path from 2.71 arrow 2 arrow 1 arrow 0 reveals exactly where the integer thresholds are crossed.
Chapter Mix
Class 12 Mathematics: Integrals