Problem Analysis #19

Grok-4.1-fast · Run 1

136.38s
20,203 toks
Problem Statement

For all x>0x > 0, let y1(x)y_1(x), y2(x)y_2(x), and y3(x)y_3(x) be the functions satisfying

dy1dx−(sin⁡x)2y1=0,y1(1)=5,\frac{dy_1}{dx} - (\sin x)^2 y_1 = 0, \quad y_1(1) = 5, dy2dx−(cos⁡x)2y2=0,y2(1)=13,\frac{dy_2}{dx} - (\cos x)^2 y_2 = 0, \quad y_2(1) = 13, dy3dx−(2−x3x3)y3=0,y3(1)=35e,\frac{dy_3}{dx} - \left(\frac{2 - x^3}{x^3}\right) y_3 = 0, \quad y_3(1) = 35e,

respectively. Find the value of

lim⁡x→0+y1(x)y2(x)y3(x)+989xx3esin⁡x.\lim_{x \to 0^+} \frac{y_1(x)y_2(x)y_3(x) + 989x}{x^3 e \sin x}.

\

Ground Truth
989
Execution Trace
Reasoning Process

[THOUGHT] The DEs are separable. The product y1 y2 y3 = 51335*e * exp(∫_1^x [sin²t + cos²t + (2-t³)/t³] dt) = 2275 e * exp(∫_1^x 2 t^{-3} dt) = 2275 e * exp([-1/t²]_1^x) = 2275 e * exp(-1/x² + 1) = 2275 e² exp(-1/x²).

The expression is [2275 e² exp(-1/x²) + 989 x] / (x³ e sin x).

As x→0+, exp(-1/x²) → 0 faster than any power of x grows, so numerator ∼ 989 x, denominator ∼ e x⁴, ratio ∼ 989/(e x³) → +∞.

To confirm with sympy, compute the limit numerically or symbolically. [/THOUGHT] [PYTHON] import sympy as sp

x = sp.symbols('x', positive=True) e = sp.E product = 2275 * e2 * sp.exp(-1/x2) num = product + 989 * x den = x**3 * e * sp.sin(x) expr = num / den lim = sp.limit(expr, x, 0, dir='+') print(lim)

Also check numerical at small x

print(float(expr.subs(x, 0.01))) print(float(expr.subs(x, 0.001))) [/PYTHON]

Tool Output
[PYTHON OUTPUT] oo 363838831.2687578 363832827957.35803 [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] The Python output confirms the limit is oo (positive infinity). This is the ground truth value of the limit. [/THOUGHT] ∞\boxed{\infty}

Explanation

The provided AI-generated answer concludes that the limit is ∞\infty, based on the Python output showing "oo" from SymPy's limit computation. The reasoning follows these steps:

  1. Solve the differential equations: Each equation is of the form dydx=p(x)y\frac{dy}{dx} = p(x) y, separable as dyy=p(x) dx\frac{dy}{y} = p(x) \, dx. The solutions are y1(x)=5exp⁡(∫1xsin⁡2t dt)y_1(x) = 5 \exp\left( \int_1^x \sin^2 t \, dt \right), y2(x)=13exp⁡(∫1xcos⁡2t dt)y_2(x) = 13 \exp\left( \int_1^x \cos^2 t \, dt \right), and y3(x)=35eexp⁡(∫1x2−t3t3 dt)y_3(x) = 35e \exp\left( \int_1^x \frac{2 - t^3}{t^3} \, dt \right).

  2. Compute the product y1(x)y2(x)y3(x)y_1(x) y_2(x) y_3(x): Note that sin⁡2t+cos⁡2t=1\sin^2 t + \cos^2 t = 1, so ∫1x(sin⁡2t+cos⁡2t) dt=x−1\int_1^x (\sin^2 t + \cos^2 t) \, dt = x - 1. For y3y_3, p3(t)=2t3−1p_3(t) = \frac{2}{t^3} - 1, so ∫1xp3(t) dt=[−1t2−t]1x=−1x2−x+2\int_1^x p_3(t) \, dt = \left[ -\frac{1}{t^2} - t \right]_1^x = -\frac{1}{x^2} - x + 2. Thus, y1y2y3=5⋅13⋅35e⋅exp⁡(x−1)⋅exp⁡(−1x2−x+2)=2275e2exp⁡(−1x2)y_1 y_2 y_3 = 5 \cdot 13 \cdot 35e \cdot \exp(x - 1) \cdot \exp\left( -\frac{1}{x^2} - x + 2 \right) = 2275 e^2 \exp\left( -\frac{1}{x^2} \right).

  3. Analyze the numerator: As x→0+x \to 0^+, exp⁡(−1x2)→0\exp\left( -\frac{1}{x^2} \right) \to 0 faster than any polynomial, making y1y2y3≈0y_1 y_2 y_3 \approx 0. The numerator simplifies to 989x+o(x)∼989x989x + o(x) \sim 989x.

  4. Analyze the denominator: x3esin⁡x∼x3ex=ex4x^3 e \sin x \sim x^3 e x = e x^4 as x→0+x \to 0^+, since sin⁡x∼x\sin x \sim x.

  5. Evaluate the limit: The expression becomes 989xex4=989ex3→+∞\frac{989x}{e x^4} = \frac{989}{e x^3} \to +\infty as x→0+x \to 0^+.

  6. Verify with Python: The code computes lim⁡x→0+2275e2exp⁡(−1/x2)+989xx3esin⁡x\lim_{x \to 0^+} \frac{2275 e^2 \exp(-1/x^2) + 989x}{x^3 e \sin x}, yielding "oo". Numerical checks at x=0.01x = 0.01 and x=0.001x = 0.001 show values increasing to approximately 3.64×1083.64 \times 10^8 and 3.64×10113.64 \times 10^{11}, confirming divergence.

This aligns with the Python output as ground truth, establishing the limit as +∞+\infty.

Final Model Output
\infty

Comparative Analysis (P19) (Average across runs)

Avg Time Taken

Gemini-3-Pro-Preview
894.8
K-EXAONE-236B-A23B
849.6
Solar-Open-100B
262.8
Deepseek-V3.2
239.3
K-EXAONE-236B-A23B
204.9
Llama-VARCO-8B-Instruct
162.1
Grok-4.1-fast
136.4
Solar-Pro-2 (31B)(high)
107.9
Kanana-2-30B-Thinking
76.7
Kanana-2-30B-Thinking-2601
68.5
GPT-5.1 (high)
51.0
A.X-4.0 (72B)
43.3
HCX-007(high)
37.2
GPT-5.2 (high)
32.8
Claude-Opus-4.5
29.2
EXAONE-4.0.1-32B (high)
5.3

Avg Token Usage

K-EXAONE-236B-A23B
70,061
K-EXAONE-236B-A23B
41,646
Solar-Open-100B
39,496
Gemini-3-Pro-Preview
28,664
Grok-4.1-fast
20,203
Solar-Pro-2 (31B)(high)
17,442
Kanana-2-30B-Thinking-2601
15,620
Deepseek-V3.2
14,643
Kanana-2-30B-Thinking
14,612
Llama-VARCO-8B-Instruct
11,147
A.X-4.0 (72B)
6,621
GPT-5.1 (high)
6,113
Claude-Opus-4.5
5,843
HCX-007(high)
4,628
GPT-5.2 (high)
4,356
EXAONE-4.0.1-32B (high)
4,114