The problem consists of four independent questions: d) Newton's Law of Cooling: The temperature of a cold drink is initially $3^\circ C$. After 30 minutes in a $15^\circ C$ room, the temperature increases to $10^\circ C$. We need to find a formula for the temperature of the cold drink after $t$ hours, and determine when the temperature will be $14^\circ C$. a) Function Analysis: Given a function $f: \{1, 2, 3\} \rightarrow \{0, 4\}$ such that $f(1) = 0$, $f(2) = 4$, and $f(3) = 4$, we need to sketch the graph of the function, find where $f$ has a local minimum value, find where $f$ has a local minimum value but not a global minimum, and find where $f$ has a global maximum value. b) Definite Integral: Given that $f$ is continuous on $R$ and $\int_0^1 f(x) dx = 3$, we need to find $\int_\pi^{\frac{5\pi}{4}} \cos(2x) f(\sin(2x)) dx$. c) Fundamental Theorem of Calculus: Given $f(x) = \int_{x^2}^{2025} (e^{y^2+1}) dy$, we need to find $f'(x)$ using the Fundamental Theorem of Calculus part 1 and then find $f'(1)$.

AnalysisDifferential EquationsNewton's Law of CoolingFunction AnalysisDefinite IntegralFundamental Theorem of CalculusCalculus
2025/6/19

1. Problem Description

The problem consists of four independent questions:
d) Newton's Law of Cooling: The temperature of a cold drink is initially 3C3^\circ C. After 30 minutes in a 15C15^\circ C room, the temperature increases to 10C10^\circ C. We need to find a formula for the temperature of the cold drink after tt hours, and determine when the temperature will be 14C14^\circ C.
a) Function Analysis: Given a function f:{1,2,3}{0,4}f: \{1, 2, 3\} \rightarrow \{0, 4\} such that f(1)=0f(1) = 0, f(2)=4f(2) = 4, and f(3)=4f(3) = 4, we need to sketch the graph of the function, find where ff has a local minimum value, find where ff has a local minimum value but not a global minimum, and find where ff has a global maximum value.
b) Definite Integral: Given that ff is continuous on RR and 01f(x)dx=3\int_0^1 f(x) dx = 3, we need to find π5π4cos(2x)f(sin(2x))dx\int_\pi^{\frac{5\pi}{4}} \cos(2x) f(\sin(2x)) dx.
c) Fundamental Theorem of Calculus: Given f(x)=x22025(ey2+1)dyf(x) = \int_{x^2}^{2025} (e^{y^2+1}) dy, we need to find f(x)f'(x) using the Fundamental Theorem of Calculus part 1 and then find f(1)f'(1).

2. Solution Steps

d) (i) Newton's Law of Cooling states that the rate of change of temperature is proportional to the difference between the object's temperature and the ambient temperature. Let T(t)T(t) be the temperature of the cold drink at time tt (in hours). Then
dTdt=k(T15)\frac{dT}{dt} = k(T - 15)
where kk is a constant. The solution to this differential equation is
T(t)=15+(T015)ektT(t) = 15 + (T_0 - 15)e^{kt}
where T0T_0 is the initial temperature. We are given that T0=3T_0 = 3, so
T(t)=15+(315)ekt=1512ektT(t) = 15 + (3 - 15)e^{kt} = 15 - 12e^{kt}.
We are also given that T(12)=10T(\frac{1}{2}) = 10. Plugging this in, we get
10=1512ek/210 = 15 - 12e^{k/2}
5=12ek/2-5 = -12e^{k/2}
ek/2=512e^{k/2} = \frac{5}{12}
k2=ln(512)\frac{k}{2} = \ln(\frac{5}{12})
k=2ln(512)k = 2\ln(\frac{5}{12})
Thus, T(t)=1512e2ln(512)t=1512(eln(512))2t=1512(512)2tT(t) = 15 - 12e^{2\ln(\frac{5}{12})t} = 15 - 12(e^{\ln(\frac{5}{12})})^{2t} = 15 - 12(\frac{5}{12})^{2t}.
(ii) We want to find tt such that T(t)=14T(t) = 14. So,
14=1512(512)2t14 = 15 - 12(\frac{5}{12})^{2t}
1=12(512)2t-1 = -12(\frac{5}{12})^{2t}
(512)2t=112(\frac{5}{12})^{2t} = \frac{1}{12}
2tln(512)=ln(112)2t \ln(\frac{5}{12}) = \ln(\frac{1}{12})
t=ln(112)2ln(512)=ln(12)2(ln(5)ln(12))2.48492(0.8755)2.48491.7511.419t = \frac{\ln(\frac{1}{12})}{2\ln(\frac{5}{12})} = \frac{-\ln(12)}{2(\ln(5) - \ln(12))} \approx \frac{-2.4849}{2(-0.8755)} \approx \frac{-2.4849}{-1.751} \approx 1.419 hours.
To the nearest hour, t=1t = 1 hour.
a) (i) The graph consists of three points: (1,0)(1, 0), (2,4)(2, 4), and (3,4)(3, 4).
(ii) A local minimum occurs at x=1x = 1 because f(1)=0f(1) = 0 is less than f(2)=4f(2) = 4.
(iii) A local minimum that is not a global minimum doesn't exist in this function, since the minimum at x=1x=1 is the global minimum as well. Thus, the answer is None.
(iv) Global maximum occurs at x=2x = 2 and x=3x = 3 since f(2)=f(3)=4f(2) = f(3) = 4 are the largest function values.
b) Let u=sin(2x)u = \sin(2x). Then du=2cos(2x)dxdu = 2\cos(2x) dx, so cos(2x)dx=12du\cos(2x) dx = \frac{1}{2} du.
When x=πx = \pi, u=sin(2π)=0u = \sin(2\pi) = 0. When x=5π4x = \frac{5\pi}{4}, u=sin(5π2)=sin(π2)=1u = \sin(\frac{5\pi}{2}) = \sin(\frac{\pi}{2}) = 1.
π5π4cos(2x)f(sin(2x))dx=01f(u)12du=1201f(u)du=12(3)=32\int_\pi^{\frac{5\pi}{4}} \cos(2x) f(\sin(2x)) dx = \int_0^1 f(u) \frac{1}{2} du = \frac{1}{2} \int_0^1 f(u) du = \frac{1}{2} (3) = \frac{3}{2}.
c) By the Fundamental Theorem of Calculus,
f(x)=ddxx22025(ey2+1)dy=e(x2)2+1ddxx2=2xex4+1f'(x) = \frac{d}{dx} \int_{x^2}^{2025} (e^{y^2+1}) dy = -e^{(x^2)^2+1} \frac{d}{dx} x^2 = -2x e^{x^4+1}.
Therefore, f(1)=2(1)e14+1=2e2f'(1) = -2(1)e^{1^4+1} = -2e^2.

3. Final Answer

d) (i) T(t)=1512(512)2tT(t) = 15 - 12(\frac{5}{12})^{2t}
(ii) 1 hour
a) (i) Graph with points (1,0), (2,4), (3,4)
(ii) x=1x = 1
(iii) None
(iv) x=2,3x = 2, 3
b) 32\frac{3}{2}
c) f(1)=2e2f'(1) = -2e^2

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