\text{Let } P_1(1+\cos t,; \sin t)\text{ be a point moving on the circle with center } (1,0)\text{ and radius } 1,]Both points start at the intersection point of the two circlesand move counterclockwise along their respective circles.Assume that their speeds satisfyLet be the time when the distance between and is maximized.At this moment, the following expression:where and are relatively prime positive integers.Find the value of .oindent
We have the two moving points:
- (P_1(t) = (1 + \cos t,; \sin t)) on the circle centered at ((1,0)) radius (1).
- (P_2(t) = (2\cos\theta(t),; 2\sin\theta(t))) on the circle centered at the origin radius (2).
Both start at ((2,0)) and move counter‑clockwise.
The speed condition is (|P_1'(t)| : |P_2'(t)| = 1 : 4) for (0 \le t \le 2\pi).
Since (|P_1'(t)| = 1) (constant), we have (|P_2'(t)| = 4).
Now (P_2'(t) = 2\theta'(t)(-\sin\theta,\cos\theta)), so (|P_2'(t)| = 2|\theta'(t)|).
Hence (2|\theta'(t)| = 4 \Rightarrow |\theta'(t)| = 2). With counter‑clockwise motion, (\theta'(t) = 2), and (\theta(0)=0) gives (\theta(t) = 2t).
Thus (P_2(t) = (2\cos 2t,; 2\sin 2t)).
We need the time (t_0) when the distance (D(t) = |P_1(t)-P_2(t)|) is maximised.
Because the square root is increasing, we maximise (S(t) = |P_1-P_2|^2).
Compute (S(t)): [ \begin{aligned} S(t) &= (1+\cos t - 2\cos 2t)^2 + (\sin t - 2\sin 2t)^2 \ &= 6 + 2\cos t - 4\bigl((1+\cos t)\cos 2t + \sin t\sin 2t\bigr) \ &= 6 + 2\cos t - 4(\cos 2t + \cos t) \qquad\text{(using the product‑to‑sum identity)} \ &= 6 + 2c - 4\bigl((2c^2-1) + c\bigr) \qquad (c = \cos t,; \cos 2t = 2c^2-1) \ &= 10 - 2c - 8c^2. \end{aligned} ]
Thus (S(t) = -8c^2 - 2c + 10) with (c = \cos t). This is a downward‑opening quadratic in (c) with vertex at (c = -\frac{1}{8}).
Since (-\frac{1}{8}\in[-1,1]), the maximum of (S(t)) occurs when (\cos t = -\frac{1}{8}).
Hence (t_0) satisfies (\cos t_0 = -\frac{1}{8}). (There are two such times in ([0,2\pi]), but the expression to evaluate depends only on (\cos t_0).)
Now evaluate the given expression at (t = t_0): [ E = 2\sin t \cdot \sin\theta(t) - (1+\cos t)\cdot 2\cos\theta(t), \qquad \theta(t)=2t. ] Substitute (\sin\theta = \sin2t = 2\sin t\cos t) and (\cos\theta = \cos2t = 2\cos^2 t-1): [ \begin{aligned} E &= 2\sin t\sin2t - 2(1+\cos t)\cos2t \ &= 4\sin^2!\cos t - 2(1+\cos t)(2\cos^2!t-1). \end{aligned} ] Using (\sin^2!t = 1 - \cos^2!t) and simplifying yields an expression solely in (c = \cos t): [ E = -8c^3 - 4c^2 + 6c + 2. ]
Now set (c = -\frac{1}{8}):
[
\begin{aligned}
c^2 = \frac{1}{64},\qquad c^3 = -\frac{1}{512}, \[2mm]
-8c^3 &= -8!\left(-\frac{1}{512}\right) = \frac{1}{64},\[2mm]
-4c^2 &= -4!\left(\frac{1}{64}\right) = -\frac{4}{64} = -\frac{1}{16},\[2mm]
6c &= 6!\left(-\frac{1}{8}\right) = -\frac{6}{8} = -\frac{48}{64},\[2mm]
+2 &= \frac{128}{64}.
\end{aligned}
]
Adding with denominator (64):
[
\frac{1}{64} - \frac{4}{64} - \frac{48}{64} + \frac{128}{64} = \frac{77}{64}.
]
Thus (E = \frac{77}{64}), so (p = 77), (q = 64) (coprime).
Therefore (p+q = 77+64 = \boxed{141}).
[THOUGHT] We need to compute the maximum of distance squared between P1(t) and P2(t), find t0, and evaluate the given expression. Let's do it step by step with Python.
We know: P1(t) = (1 + cos t, sin t) P2(t) = (2 cos 2t, 2 sin 2t) [since θ = 2t]
Distance squared: S(t) = (1 + cos t - 2 cos 2t)^2 + (sin t - 2 sin 2t)^2.
We can simplify symbolically or evaluate numerically. We expect maximum at cos t = -1/8.
We'll compute S(t) for t in [0, 2π], find t0 where S is max, then compute E = 2 sin t sin(2t) - 2(1+cos t) cos(2t) at t0.
Let's code. [/THOUGHT]
[PYTHON] import numpy as np
Define the distance squared function
def S(t): return (1 + np.cos(t) - 2np.cos(2t))**2 + (np.sin(t) - 2np.sin(2t))**2
Sample many points to find approximate t0
t_vals = np.linspace(0, 2*np.pi, 1000001) S_vals = S(t_vals) max_idx = np.argmax(S_vals) t0 = t_vals[max_idx] print("t0 (approx):", t0) print("cos(t0):", np.cos(t0))
Now compute E at t0
c = np.cos(t0)
Using exact expression: E = -8c^3 - 4c^2 + 6c + 2
E = -8c**3 - 4c**2 + 6*c + 2 print("E (approx):", E)
Alternatively, compute directly from trig:
theta = 2t0 E_direct = 2np.sin(t0)np.sin(theta) - 2(1+np.cos(t0))*np.cos(theta) print("E_direct (approx):", E_direct) </PYTHON>
[THOUGHT] Let's redo the code correctly.
[PYTHON] import numpy as np
Define the distance squared function
def S(t): return (1 + np.cos(t) - 2np.cos(2t))**2 + (np.sin(t) - 2np.sin(2t))**2
Sample many points to find approximate t0
t_vals = np.linspace( univers0.52, 1)
We'll sample t from 0 to 2π.
Let's compute: </think>
[THOUGHT] Let's redo the code carefully.
[PYTHON] import numpy as np
Define the distance squared function
def S(t): return (1 + np.cos(t) - 2np.cos(2t))**2 + (np.sin(t) - 2np.sin(2t))**2
Sample many points to find approximate t0
t_vals = np.linspace(0, 2*np.pi, 1000001) S_vals = S(t_vals) max_idx = np.argmax(S_vals) t0 = t_vals[max_idx] print("t0 (approx):", t0) print("cos(t0):", np.cos(t0))
Now compute E at t0
c = np.cos(t0)
Using exact expression: E = -8c^3 - 4c^2 + 6c + 2
E = -8c**3 - 4c**2 + 6*c + 2 print("E (approx):", E)
Alternatively, compute directly from trig:
theta = 2t0 E_direct = 2np.sin(t0)np.sin(theta) - 2(1+np.cos(t0))*np.cos(theta) print("E_direct (approx):", E_direct) [/PYTHON]
[TH]
[THOUGHT] We compute E exactly using fractions to verify p/q = 77/64.
[PYTHON] from fractions import Fraction c = Fraction(-1, 8) E = -8c**3 - 4c**2 + 6*c + 2 print(E) print(E.numerator, E.denominator) print("p+q =", E.numerator + E.denominator) [/PYTHON] </think>
[THOUGHT] We compute E exactly using fractions to verify p/q = 77/64.
[PYTHON] from fractions import Fraction c = Fraction(-1, 8) E = -8c**3 - 4c**2 + 6*c + 2 print(E) print("p+q =", E.numerator + E.denominator) [/PYTHON]
[THOUGHT]
The expression evaluates to ( \frac{77}{64} ), with (p=77) and (q=64) relatively prime. Therefore (p+q = 77+64 = 141).
\boxed{141}