Problem Analysis #20

K-EXAONE-236B-A23B · Run 1

64.23s
6,115 toks
Problem Statement

Let a function f(x)f(x) defined on the set of all real numbers satisfy

f(x)=xsin(πx)for x[0,2],f(x) = x \sin(\pi x) \qquad \text{for } x \in [0,2],

and

f(x)=2f(x2)for all real x.f(x) = 2 f(x-2) \qquad \text{for all real } x.

Consider the region enclosed by the curve y=f(x)y = f(x), the line

y=21012(x2026),y = 2^{1012}(x - 2026),

and the two vertical lines x=2026x = 2026 and x=2027x = 2027.The area of this region is equal to

21012(p+qπ+r3π),2^{1012}\left(p + \frac{q}{\pi} + \frac{r\sqrt{3}}{\pi}\right),

for some rational numbers p,q,rp, q, r.Find the value of 2028pqr2028 \cdot p \cdot q \cdot r.oindent

Ground Truth
1352
Execution Trace
Reasoning Process

[THOUGHT] We need to understand the problem fully. There's a piecewise-defined function f(x):

  • For x in [0,2], f(x) = x sin(πx).
  • For all real x, f(x) = 2 f(x-2).

This is a functional equation that defines f recursively. Let's interpret: For any x, we can subtract multiples of 2 to bring it into [0,2], but each time we subtract 2, we multiply the function value by 2.

Specifically, for any integer n such that x - 2n ∈ [0,2], we have f(x) = 2^n f(x - 2n). But careful: The equation f(x) = 2 f(x-2) holds for all real x. That means f(x) = 2 f(x-2). Applying repeatedly: f(x) = 2^k f(x - 2k) for any integer k. So if we choose k such that x - 2k ∈ [0,2], then f(x) = 2^k f(x - 2k).

Now we consider region enclosed by curve y = f(x), line y = 2^{1012}(x - 2026), vertical lines x = 2026 and x = 2027. So region is between these two curves from x=2026 to x=2027.

We need area of that region. Area = ∫_{2026}^{2027} |f(x) - 2^{1012}(x - 2026)| dx? Actually region enclosed by those four curves: likely the region bounded above/below by them. Since both curves are defined, we need the absolute difference between them integrated.

But we need to know which is above which. Let's compute f(x) on [2026,2027]. Since 2026 is even? 2026/2 = 1013, so 2026 = 21013. So x in [2026,2027] corresponds to subtracting 21013 = 2026? Wait, we need to bring x into [0,2] by subtracting multiples of 2.

Let x = 2026 + t, where t ∈ [0,1]. Then x - 2*1013 = 2026 + t - 2026 = t ∈ [0,1] which is subset of [0,2]. So k = 1013. Then f(x) = 2^{1013} f(t) = 2^{1013} * t sin(π t) (since t ∈ [0,1] ⊂ [0,2] and sin(π t) is sin(π t)).

Thus f(x) = 2^{1013} * t sin(π t) where t = x - 2026.

Now the line is y = 2^{1012} (x - 2026) = 2^{1012} t.

So we have f(x) = 2^{1013} t sin(π t) and line L(x) = 2^{1012} t.

Factor 2^{1012}: f(x) = 2^{1012} * 2 * t sin(π t) = 2^{1012} * 2 t sin(π t).

Thus difference: f(x) - L(x) = 2^{1012} t (2 sin(π t) - 1).

Now we need area between curves from t=0 to t=1. But which curve is above? Let's check sign: For t in [0,1], sin(π t) ≥ 0, so 2 sin(π t) ≥ 0. But 2 sin(π t) - 1 could be positive or negative depending on t.

Find where 2 sin(π t) - 1 = 0 → sin(π t) = 1/2 → π t = π/6 or 5π/6 within [0,π] (since t∈[0,1], πt∈[0,π]). So t = 1/6 or t = 5/6.

Thus for t ∈ [0,1/6), sin(π t) < 1/2 → 2 sin(π t) - 1 < 0 → f(x) < L(x). For t ∈ (1/6,5/6), sin(π t) > 1/2 → f(x) > L(x). For t ∈ (5/6,1], sin(π t) < 1/2 → f(x) < L(x).

Thus the region enclosed by the two curves and vertical lines x=2026 and x=2027 is the region between them, but we need to compute area as the integral of absolute difference. So area = ∫_{t=0}^{1} |2^{1012} t (2 sin(π t) - 1)| dt = 2^{1012} ∫_0^1 t |2 sin(π t) - 1| dt.

Given answer format: area = 2^{1012} (p + q/π + r√3/π). So we need to compute I = ∫_0^1 t |2 sin(π t) - 1| dt, express as p + q/π + r√3/π, where p,q,r rational.

Then area = 2^{1012} * I.

Finally, we need 2028 * p * q * r.

We need to compute I exactly.

Let’s compute I = ∫_0^1 t |2 sin(π t) - 1| dt.

Split intervals: [0,1/6], [1/6,5/6], [5/6,1].

Define g(t) = 2 sin(π t) - 1.

On [0,1/6], g(t) ≤ 0, so |g(t)| = -g(t) = 1 - 2 sin(π t). On [1/6,5/6], g(t) ≥ 0, so |g(t)| = g(t) = 2 sin(π t) - 1. On [5/6,1], g(t) ≤ 0, so |g(t)| = -g(t) = 1 - 2 sin(π t).

Thus I = ∫0^{1/6} t (1 - 2 sin(π t)) dt + ∫{1/6}^{5/6} t (2 sin(π t) - 1) dt + ∫_{5/6}^{1} t (1 - 2 sin(π t)) dt.

We can compute each integral analytically using integration by parts or symbolic integration.

Let’s compute using Python with sympy to get exact expression.

We'll compute I = ∫_0^1 t |2 sin(π t) - 1| dt.

We'll compute each piece and sum.

Let’s write Python code.

[PYTHON] import sympy as sp

t = sp.symbols('t', real=True)

Define integrand piecewise

f1 = t * (1 - 2sp.sin(sp.pit)) # 0 to 1/6 f2 = t * (2sp.sin(sp.pit) - 1) # 1/6 to 5/6 f3 = t * (1 - 2sp.sin(sp.pit)) # 5/6 to 1

Integrate

I1 = sp.integrate(f1, (t, 0, sp.Rational(1,6))) I2 = sp.integrate(f2, (t, sp.Rational(1,6), sp.Rational(5,6))) I3 = sp.integrate(f3, (t, sp.Rational(5,6), 1))

I = sp.simplify(I1 + I2 + I3) I [/PYTHON]

But careful: sp.integrate may give expression with π and sqrt(3). Let's run.

We'll also compute numeric to check.

Let's execute. </think>

[PYTHON] import sympy as sp

t = sp.symbols('t', real=True)

Define integrand piecewise

f1 = t * (1 - 2sp.sin(sp.pit)) # 0 to 1/6 f2 = t * (2sp.sin(sp.pit) - 1) # 1/6 to 5/6 f3 = t * (1 - 2sp.sin(sp.pit)) # 5/6 to 1

Integrate

I1 = sp.integrate(f1, (t, 0, sp.Rational(1,6))) I2 = sp.integrate(f2, (t, sp.Rational(1,6), sp.Rational(5,6))) I3 = sp.integrate(f3, (t, sp.Rational(5,6), 1))

I = sp.simplify(I1 + I2 + I3) I [/PYTHON]

Tool Output
[PYTHON OUTPUT] (-12 - pi + 12*sqrt(3))/(6*pi) [/PYTHON OUTPUT] [PYTHON OUTPUT] (-12 - pi + 12*sqrt(3))/(6*pi) [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] The Python output gives the value of the integral as (12π+123)/(6π)(-12 - \pi + 12\sqrt{3})/(6\pi). This is the area of one period of the function's envelope relative to the line y=ty = t? Wait, the problem's region is between y=f(x)y = f(x) and y=21012(x2026)y = 2^{1012}(x - 2026) from x=2026x = 2026 to 20272027. But ff is periodic with period 2 and scaled by 210122^{1012} horizontally? Actually f(x)=2f(x2)f(x) = 2 f(x-2) means f(x+2)=f(x)/2f(x+2) = f(x)/2? Let's check: f(x)=2f(x2)f(x) = 2 f(x-2) implies f(x+2)=f(x)/2f(x+2) = f(x)/2? No: replace xx by x+2x+2: f(x+2)=2f(x)f(x+2) = 2 f(x). So it's doubling when shifting right by 2. That means f(x+2)=2f(x)f(x+2) = 2 f(x). So over each period of length 2, the function is scaled by factor 2. But the problem says f(x)=2f(x2)f(x) = 2 f(x-2) for all real xx. That means f(x+2)=2f(x)f(x+2) = 2 f(x). So ff grows by factor 2 every 2 units.

Given f(x)=xsin(πx)f(x) = x \sin(\pi x) on [0,2][0,2], we can shift to other intervals: For x[2,4]x \in [2,4], f(x)=2f(x2)=2(x2)sin(π(x2))f(x) = 2 f(x-2) = 2 (x-2) \sin(\pi (x-2)). But sin(π(x2))=sin(πx2π)=sin(πx)\sin(\pi(x-2)) = \sin(\pi x - 2\pi) = \sin(\pi x). So f(x)=2(x2)sin(πx)f(x) = 2 (x-2) \sin(\pi x) for x[2,4]x \in [2,4]. Similarly, for x[2026,2028]x \in [2026, 2028], f(x)=21013(x2026)sin(πx)f(x) = 2^{1013} (x - 2026) \sin(\pi x)? Let's derive: For x[2,4]x \in [2,4], f(x)=2f(x2)=2(x2)sin(π(x2))=2(x2)sin(πx)f(x) = 2 f(x-2) = 2 (x-2) \sin(\pi (x-2)) = 2 (x-2) \sin(\pi x). For x[4,6]x \in [4,6], f(x)=2f(x2)=2[2(x4)sin(πx)]=4(x4)sin(πx)f(x) = 2 f(x-2) = 2 \cdot [2 (x-4) \sin(\pi x)] = 4 (x-4) \sin(\pi x). So in general, for x[2k,2k+2]x \in [2k, 2k+2], f(x)=2k(x2k)sin(πx)f(x) = 2^k (x - 2k) \sin(\pi x). Here 2026=210132026 = 2 \cdot 1013, so k=1013k = 1013. Then f(x)=21013(x2026)sin(πx)f(x) = 2^{1013} (x - 2026) \sin(\pi x) for x[2026,2028]x \in [2026, 2028]. The region is between y=f(x)y = f(x) and y=21012(x2026)y = 2^{1012}(x - 2026) from x=2026x = 2026 to 20272027.

Thus the difference is f(x)21012(x2026)=[21013(x2026)sin(πx)21012(x2026)]=21012(x2026)[2sin(πx)1]f(x) - 2^{1012}(x - 2026) = [2^{1013}(x - 2026) \sin(\pi x) - 2^{1012}(x - 2026)] = 2^{1012}(x - 2026)[2 \sin(\pi x) - 1].

We need the area between these curves from x=2026x = 2026 to 20272027. That's 2026202721012(x2026)[2sin(πx)1]dx\int_{2026}^{2027} |2^{1012}(x - 2026)[2 \sin(\pi x) - 1]| \, dx. But sign changes? Let t=x2026t = x - 2026, then t[0,1]t \in [0,1], and sin(πx)=sin(π(t+2026))=sin(πt+2026π)\sin(\pi x) = \sin(\pi(t + 2026)) = \sin(\pi t + 2026\pi). Since 20262026 is even, 2026π2026\pi is multiple of 2π2\pi, so sin(πt+2026π)=sin(πt)\sin(\pi t + 2026\pi) = \sin(\pi t). So the integrand becomes 21012t[2sin(πt)1]2^{1012} t [2 \sin(\pi t) - 1].

The area between the curves is 0121012t(2sin(πt)1)dt=2101201t(2sin(πt)1)dt\int_0^1 |2^{1012} t (2 \sin(\pi t) - 1)| dt = 2^{1012} \int_0^1 |t (2 \sin(\pi t) - 1)| dt.

The earlier Python computed 01t(12sin(πt))dt\int_0^1 |t (1 - 2 \sin(\pi t))| dt? Wait, they defined f1 = t*(1 - 2sin(pit)) for 0 to 1/6, f2 = t*(2sin(pit) - 1) for 1/6 to 5/6, f3 = t*(1 - 2sin(pit)) for 5/6 to 1. That matches t(2sin(πt)1)|t (2\sin(\pi t) - 1)| because:

For t[0,1/6]t \in [0,1/6], 2sin(πt)102\sin(\pi t) - 1 \le 0? Let's check: at t=0t=0, 2sin01=1<02\sin 0 - 1 = -1 < 0. At t=1/6t=1/6, 2sin(π/6)1=2(1/2)1=02\sin(\pi/6) - 1 = 2*(1/2) - 1 = 0. So on [0,1/6][0,1/6], 2sin(πt)102\sin(\pi t) - 1 \le 0, so t(2sin(πt)1)=t(12sin(πt))|t (2\sin(\pi t) - 1)| = t(1 - 2\sin(\pi t)). That's f1.

For t[1/6,5/6]t \in [1/6, 5/6], 2sin(πt)102\sin(\pi t) - 1 \ge 0? At t=1/2t=1/2, 2sin(π/2)1=21=1>02\sin(\pi/2) - 1 = 2 - 1 = 1 > 0. At t=5/6t=5/6, 2sin(5π/6)1=2(1/2)1=02\sin(5\pi/6) - 1 = 2*(1/2) - 1 = 0. So 2sin(πt)102\sin(\pi t) - 1 \ge 0 on [1/6,5/6][1/6, 5/6], so t(2sin(πt)1)=t(2sin(πt)1)|t (2\sin(\pi t) - 1)| = t(2\sin(\pi t) - 1). That's f2.

For t[5/6,1]t \in [5/6, 1], 2sin(πt)102\sin(\pi t) - 1 \le 0? At t=1t=1, 2sin(π)1=1<02\sin(\pi) - 1 = -1 < 0. So t(2sin(πt)1)=t(12sin(πt))|t (2\sin(\pi t) - 1)| = t(1 - 2\sin(\pi t)). That's f3.

Thus the Python computed exactly A=01t(2sin(πt)1)dt=(12π+123)/(6π)A = \int_0^1 |t (2\sin(\pi t) - 1)| dt = (-12 - \pi + 12\sqrt{3})/(6\pi).

Thus the area of the region is 21012A=2101212π+1236π2^{1012} \cdot A = 2^{1012} \cdot \frac{-12 - \pi + 12\sqrt{3}}{6\pi}.

The problem says this area equals 21012(p+qπ+r3π)2^{1012} \left(p + \frac{q}{\pi} + \frac{r\sqrt{3}}{\pi}\right).

So equate: 12π+1236π=p+qπ+r3π\frac{-12 - \pi + 12\sqrt{3}}{6\pi} = p + \frac{q}{\pi} + \frac{r\sqrt{3}}{\pi}.

Multiply by 1: p+qπ+r3π=126ππ6π+1236π=2π16+23πp + \frac{q}{\pi} + \frac{r\sqrt{3}}{\pi} = \frac{-12}{6\pi} - \frac{\pi}{6\pi} + \frac{12\sqrt{3}}{6\pi} = \frac{-2}{\pi} - \frac{1}{6} + \frac{2\sqrt{3}}{\pi}.

Thus p=1/6p = -1/6, q/π=2/πq=2q/\pi = -2/\pi \Rightarrow q = -2, r3/π=23/πr=2r\sqrt{3}/\pi = 2\sqrt{3}/\pi \Rightarrow r = 2.

So p=1/6p = -1/6, q=2q = -2, r=2r = 2.

Then 2028pqr=2028(1/6)(2)22028 \cdot p \cdot q \cdot r = 2028 \cdot (-1/6) \cdot (-2) \cdot 2.

Compute: (1/6)(2)=1/3(-1/6) \cdot (-2) = 1/3. Then (1/3)2=2/3(1/3) \cdot 2 = 2/3. Then 2028(2/3)=2028/32=6762=13522028 \cdot (2/3) = 2028/3 \cdot 2 = 676 \cdot 2 = 1352.

Thus final answer is 1352.

1352\boxed{1352}

Final Model Output
1352

Comparative Analysis (P20) (Average across runs)

Avg Time Taken

K-EXAONE-236B-A23B
1117.7
Solar-Open-100B
743.0
Solar-Pro-2 (31B)(high)
209.1
Llama-VARCO-8B-Instruct
194.6
Gemini-3-Pro-Preview
117.1
A.X-4.0 (72B)
98.1
Grok-4.1-fast
91.6
Kanana-2-30B-Thinking
82.5
HCX-007(high)
65.9
K-EXAONE-236B-A23B
64.2
GPT-5.1 (high)
59.3
Deepseek-V3.2
40.9
Kanana-2-30B-Thinking-2601
39.3
Claude-Opus-4.5
27.1
GPT-5.2 (high)
22.2
EXAONE-4.0.1-32B (high)
7.6

Avg Token Usage

K-EXAONE-236B-A23B
231,341
Solar-Open-100B
23,307
Kanana-2-30B-Thinking
15,652
Grok-4.1-fast
15,328
Gemini-3-Pro-Preview
13,814
Solar-Pro-2 (31B)(high)
12,507
Kanana-2-30B-Thinking-2601
9,180
HCX-007(high)
7,833
GPT-5.1 (high)
7,486
Deepseek-V3.2
7,264
Llama-VARCO-8B-Instruct
7,065
K-EXAONE-236B-A23B
6,115
GPT-5.2 (high)
5,568
Claude-Opus-4.5
5,400
EXAONE-4.0.1-32B (high)
5,036
A.X-4.0 (72B)
3,005