Problem Analysis #8

42.73s
12,309 toks
Problem Statement

Answer the following questions. Here, for any complex value zz, zˉ\bar{z} is the complex conjugate of zz, argz\arg z is the argument of zz, z|z| is the absolute value of zz, and ii is the imaginary unit.\subsection*{I.}Sketch the region of zz on the complex plane that satisfieszzˉ+2(z+zˉ)+3i(zzˉ)+20.z\bar{z} + \sqrt{2}(z + \bar{z}) + 3i(z - \bar{z}) + 2 \leq 0.\subsection*{II.}Consider the complex-valued functionf(z)=z22(z2+2i)z2.f(z) = \frac{z^2 - 2}{(z^2 + 2i)z^2}.

  • [(1)] Find all the poles of f(z)f(z) as well as the orders and residues at the poles.

  • [(2)] By applying the residue theorem, find the value of the integral I1=Cf(z)dz, I_1 = \oint_C f(z)\,dz, where the integration path CC is the circle in the counterclockwise direction given by z+1=2|z + 1| = 2. \subsection*{III.}

  • [(1)] Let g(z)g(z) be a complex-valued function satisfying limzg(z)=0 \lim_{|z|\to\infty} g(z) = 0 for 0 $$\leq$$ \arg z $$\leq$$ $$\pi$$$. Let C_Rbethesemicircle,withradiusbe the semicircle, with radiusR, in the upper half of the complex plane with center at the origin. Show that $$ \lim_{R\to\infty} \int_{C_R} e^{iaz} g(z)\,dz = 0, $$ where a$ is a positive real number.

  • [(2)] Find the value of the integral I2=0sinxxdx. I_2 = \int_0^{\infty} \frac{\sin x}{x}\,dx. \subsection*{IV. Final quantity}In I, the region for zz is a disk. Let RR be its radius and cc be its center. In II(2), let RinR_{\mathrm{in}} be the sum of the residues of f(z)f(z) over all poles lying inside the circle z+1=2|z + 1| = 2. In II(2) and III(2), let I1I_1 and I2I_2 be the values of the corresponding integrals.DefineS:=(R2+c2)2(I1I2)31Rin,K:=999S2+7.S := (R^2 + |c|^2)^2 \left(\frac{|I_1|}{I_2}\right)^3 \cdot \frac{1}{|R_{\mathrm{in}}|},\qquad\mathcal{K} := 999\,S^2 + 7.Compute the integer K\mathcal{K}.\

Ground Truth
40919040007
Execution Trace
Reasoning Process

[THOUGHT] Let me solve this problem step by step.

Part I: Finding the region Given: zzˉ+2(z+zˉ)+3i(zzˉ)+20z\bar{z} + \sqrt{2}(z + \bar{z}) + 3i(z - \bar{z}) + 2 \leq 0

Let z=x+iyz = x + iy, then:

  • zzˉ=x2+y2z\bar{z} = x^2 + y^2
  • z+zˉ=2xz + \bar{z} = 2x
  • zzˉ=2iyz - \bar{z} = 2iy

Substituting: x2+y2+2(2x)+3i(2iy)+20x^2 + y^2 + \sqrt{2}(2x) + 3i(2iy) + 2 \leq 0 x2+y2+22x6y+20x^2 + y^2 + 2\sqrt{2}x - 6y + 2 \leq 0

Completing the square: (x+2)22+(y3)29+20(x + \sqrt{2})^2 - 2 + (y - 3)^2 - 9 + 2 \leq 0 (x+2)2+(y3)29(x + \sqrt{2})^2 + (y - 3)^2 \leq 9

So the center is c=2+3ic = -\sqrt{2} + 3i and radius R=3R = 3.

Part II: Finding poles and residues of f(z)=z22(z2+2i)z2f(z) = \frac{z^2 - 2}{(z^2 + 2i)z^2}

Poles:

  • z=0z = 0 (from z2z^2) - order 2
  • z2+2i=0z2=2i=2eiπ/2z^2 + 2i = 0 \Rightarrow z^2 = -2i = 2e^{-i\pi/2}
    • z=2eiπ/4=1iz = \sqrt{2}e^{-i\pi/4} = 1 - i
    • z=2ei3π/4=1+iz = \sqrt{2}e^{i3\pi/4} = -1 + i

For the circle z+1=2|z + 1| = 2:

  • Center at 1-1, radius 22
  • Check which poles are inside

Let me compute this with Python. [/THOUGHT] [PYTHON] import numpy as np from sympy import *

Part I

Center c = -sqrt(2) + 3i, radius R = 3

R = 3 c = -sqrt(2) + 3*I c_abs = Abs(c) print(f"Part I: R = {R}, c = {c}, |c| = {simplify(c_abs)}") print(f"|c|^2 = {simplify(c_abs**2)}")

Part II

z = symbols('z') f = (z2 - 2) / ((z2 + 2*I) * z**2)

Find poles

z = 0 is a pole of order 2

z^2 + 2i = 0 => z = sqrt(-2i)

-2i = 2exp(-ipi/2)

sqrt(-2i) = sqrt(2)exp(-ipi/4) = sqrt(2)(cos(-pi/4) + isin(-pi/4)) = 1 - i

and sqrt(2)exp(i3pi/4) = sqrt(2)(cos(3pi/4) + isin(3*pi/4)) = -1 + i

pole1 = 0 pole2 = 1 - I # sqrt(-2i) pole3 = -1 + I # -sqrt(-2i)

print(f"\nPoles: z = {pole1}, z = {pole2}, z = {pole3}")

Verify poles

print(f"Check pole2: (1-i)^2 + 2i = {expand((1-I)**2 + 2I)}") print(f"Check pole3: (-1+i)^2 + 2i = {expand((-1+I)**2 + 2I)}")

Check which poles are inside |z + 1| = 2

Distance from pole to -1

dist1 = Abs(pole1 - (-1)) dist2 = Abs(pole2 - (-1)) dist3 = Abs(pole3 - (-1))

print(f"\nDistance from poles to -1:") print(f"|0 - (-1)| = {dist1}") print(f"|(1-i) - (-1)| = {simplify(dist2)}") print(f"|(-1+i) - (-1)| = {simplify(dist3)}")

Poles inside: those with distance < 2

print(f"\nPoles inside |z+1| = 2:") print(f"z = 0: {dist1} < 2 ? {dist1 < 2}") print(f"z = 1-i: {simplify(dist2)} < 2 ? {simplify(dist2) < 2}") print(f"z = -1+i: {simplify(dist3)} < 2 ? {simplify(dist3) < 2}") [/PYTHON]

Tool Output
[PYTHON OUTPUT] Part I: R = 3, c = -sqrt(2) + 3*I, |c| = sqrt(11) |c|^2 = 11 Poles: z = 0, z = 1 - I, z = -1 + I Check pole2: (1-i)^2 + 2i = 0 Check pole3: (-1+i)^2 + 2i = 0 Distance from poles to -1: |0 - (-1)| = 1 |(1-i) - (-1)| = sqrt(5) |(-1+i) - (-1)| = 1 Poles inside |z+1| = 2: z = 0: 1 < 2 ? True z = 1-i: sqrt(5) < 2 ? False z = -1+i: 1 < 2 ? True [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] Let me continue computing the residues and integrals. [/THOUGHT] [PYTHON] from sympy import *

z = symbols('z') f = (z2 - 2) / ((z2 + 2*I) * z**2)

Residues

At z = 0 (pole of order 2)

Res = lim_{z->0} d/dz [z^2 * f(z)] = lim d/dz [(z^2 - 2)/(z^2 + 2i)]

g0 = (z2 - 2)/(z2 + 2*I) dg0 = diff(g0, z) res_0 = limit(dg0, z, 0) print(f"Residue at z = 0: {simplify(res_0)}")

At z = -1 + i (simple pole)

Res = lim_{z -> -1+i} (z - (-1+i)) * f(z)

f(z) = (z^2 - 2) / ((z - (1-i))(z - (-1+i)) * z^2)

At simple pole z0: Res = (z0^2 - 2) / ((z0 - (1-i)) * z0^2 * 2*z0)

Actually z^2 + 2i = (z - (1-i))(z - (-1+i))

So Res at z = -1+i is (z^2 - 2) / (2z * z^2) evaluated at z = -1+i

pole3 = -1 + I numerator_at_pole3 = (pole32 - 2) derivative_denom = 2*z # derivative of z^2 + 2i denom_at_pole3 = derivative_denom.subs(z, pole3) * pole32 res_pole3 = simplify(numerator_at_pole3 / denom_at_pole3) print(f"Residue at z = -1+i: {res_pole3}")

Let me compute more carefully using residue function

res_0_sympy = residue(f, z, 0) res_pole3_sympy = residue(f, z, -1+I) res_pole2_sympy = residue(f, z, 1-I)

print(f"\nUsing sympy residue:") print(f"Residue at z = 0: {simplify(res_0_sympy)}") print(f"Residue at z = -1+i: {simplify(res_pole3_sympy)}") print(f"Residue at z = 1-i: {simplify(res_pole2_sympy)}")

Sum of residues inside |z+1| = 2 (poles: z=0 and z=-1+i)

R_in = res_0_sympy + res_pole3_sympy print(f"\nR_in = {simplify(R_in)}") print(f"|R_in| = {simplify(Abs(R_in))}")

I_1 = 2pii * R_in

I_1 = 2 * pi * I * R_in print(f"\nI_1 = {simplify(I_1)}") print(f"|I_1| = {simplify(Abs(I_1))}")

Part III(2): I_2 = integral from 0 to infinity of sin(x)/x dx = pi/2

I_2 = pi/2 print(f"\nI_2 = {I_2}")

Final calculation

R = 3 c_abs_sq = 11 # |c|^2 = 2 + 9 = 11 R_sq_plus_c_sq = R**2 + c_abs_sq # 9 + 11 = 20

print(f"\nR^2 + |c|^2 = {R_sq_plus_c_sq}") print(f"(R^2 + |c|^2)^2 = {R_sq_plus_c_sq**2}")

Compute S

abs_I1 = simplify(Abs(I_1)) abs_R_in = simplify(Abs(R_in))

print(f"\n|I_1| = {abs_I1}") print(f"|R_in| = {abs_R_in}") print(f"I_2 = {I_2}")

S = (R^2 + |c|^2)^2 * (|I_1|/I_2)^3 * 1/|R_in|

S = (R_sq_plus_c_sq**2) * (abs_I1/I_2)**3 / abs_R_in S_simplified = simplify(S) print(f"\nS = {S_simplified}")

K = 999 * S^2 + 7

K = 999 * S_simplified**2 + 7 K_simplified = simplify(K) print(f"\nK = {K_simplified}") [/PYTHON]

Tool Output
[PYTHON OUTPUT] Residue at z = 0: 0 Residue at z = -1+i: -1/2 Using sympy residue: Residue at z = 0: 0 Residue at z = -1+i: -1/2 Residue at z = 1-i: 1/2 R_in = -1/2 |R_in| = 1/2 I_1 = -I*pi |I_1| = pi I_2 = pi/2 R^2 + |c|^2 = 20 (R^2 + |c|^2)^2 = 400 |I_1| = pi |R_in| = 1/2 I_2 = pi/2 S = 6400 K = 40919040007 [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] The Python calculation gives us:

  • R = 3, |c|² = 11, so R² + |c|² = 20
  • R_in = -1/2, so |R_in| = 1/2
  • I_1 = -iπ, so |I_1| = π
  • I_2 = π/2

S = (20)² × (π/(π/2))³ × (1/(1/2)) = 400 × 8 × 2 = 6400

K = 999 × 6400² + 7 = 999 × 40960000 + 7 = 40919040000 + 7 = 40919040007 [/THOUGHT]

\boxed{40919040007}

Final Model Output
40919040007

Comparative Analysis (P8) (Average across runs)

Avg Time Taken

Gemini-3-Pro-Preview
276.8
Deepseek-V3.2
202.1
GPT-5.1 (high)
91.6
Llama-VARCO-8B-Instruct
63.3
Grok-4.1-fast
60.2
A.X-4.0 (72B)
58.6
Claude-Opus-4.5
42.7
Solar-Pro-2 (31B)(high)
41.8
HCX-007(high)
20.4
EXAONE-4.0.1-32B (high)
5.5

Avg Token Usage

Gemini-3-Pro-Preview
15034.0
Claude-Opus-4.5
12309.0
Grok-4.1-fast
10596.0
Solar-Pro-2 (31B)(high)
9159.0
A.X-4.0 (72B)
9042.0
GPT-5.1 (high)
8139.0
Deepseek-V3.2
8047.0
HCX-007(high)
5016.0
EXAONE-4.0.1-32B (high)
4747.0
Llama-VARCO-8B-Instruct
1832.0