Consider the curve given in polar coordinates bywith the origin as the pole and the positive –axis as the initial line.
- [(1)] Compute the area of the region enclosed by the curve .
- [(2)] At the point find the slope of the tangent line to the curve in the –coordinate plane. Let be the value obtained in part (1). Express the answer from part (2) in the formwhere and are integers, and let those integers be the definitions of and . Using these values of , , and , compute\
[THOUGHT] I will:
- Use the polar area formula (a = \frac12 \int_0^{2\pi} r^2 , d\theta) with (r = 2+\cos\theta).
- Use the polar slope formula (\frac{dy}{dx} = \frac{r' \sin\theta + r\cos\theta}{r' \cos\theta - r\sin\theta}) and evaluate at (\theta = \frac{\pi}{4}), where (r = \frac{4+\sqrt2}{2}).
- Simplify the slope into the form (b + \sqrt{c}) and read off integers (b,c).
- Compute (\frac{abc}{\pi}) using the area (a) from (1).
I’ll use Sympy to carry out the integrals and algebra exactly. [/THOUGHT] [PYTHON] import sympy as sp
Define symbols
theta = sp.symbols('theta', real=True) r = 2 + sp.cos(theta)
Part (1): area
area = sp.simplify(sp.Rational(1,2) * sp.integrate(r**2, (theta, 0, 2*sp.pi))) print("Area a =", area)
Part (2): slope dy/dx at the given point (theta = pi/4)
theta0 = sp.pi/4 r0 = r.subs(theta, theta0) dr_dtheta = sp.diff(r, theta) dr0 = dr_dtheta.subs(theta, theta0)
slope = sp.simplify((dr_dthetasp.sin(theta) + rsp.cos(theta)) / (dr_dthetasp.cos(theta) - rsp.sin(theta))) slope0 = sp.simplify(slope.subs(theta, theta0)) print("Slope at theta=pi/4 =", slope0)
Express slope as b + sqrt(c)
b, c = sp.symbols('b c', integer=True)
Let's see if slope0 can be written as A + B*sqrt(2) first
slope_simplified = sp.nsimplify(slope0, [sp.sqrt(2), sp.sqrt(3), sp.sqrt(5)]) print("nsimplify slope:", slope_simplified)
It appears to be of form p + q*sqrt(2); we need b + sqrt(c).
If it's p + qsqrt(2), then set qsqrt(2) = sqrt(c) => c = 2*q^2 if q>0.
p, q = sp.symbols('p q') p_q_form = sp.together(slope_simplified).expand() print("Expanded slope form:", p_q_form)
Manually decompose assuming form A + B*sqrt(2)
A = sp.simplify(sp.radsimp(sp.simplify(sp.nsimplify(slope0 - sp.sqrt(2)*0, [sp.sqrt(2)])))) print("Test A (not final):", A)
Directly solve for coefficients in basis {1, sqrt(2)}
A_coeff = sp.simplify(sp.nsimplify((slope0.expand().rewrite(sp.sqrt) - sp.sqrt(2)*0), [sp.sqrt(2)])) print("A_coeff tentative:", A_coeff)
Let's just ask sympy to express in a + b*sqrt(2)
a_sym, b_sym = sp.symbols('a_sym b_sym') A_expr = sp.solve(sp.Eq(a_sym + b_sym*sp.sqrt(2), slope0), (a_sym, b_sym))[0] print("Decomposition (a_sym, b_sym) with sqrt(2):", A_expr)
a_sym_val, b_sym_val = A_expr
Now want b + sqrt(c) with integers; set b = a_sym_val, sqrt(c) = b_sym_val*sqrt(2)
b_int = sp.simplify(a_sym_val) sqrt_c_expr = sp.simplify(b_sym_val*sp.sqrt(2)) print("b_int =", b_int, ", sqrt_c_expr =", sqrt_c_expr)
Then c is square of coefficient inside sqrt_c_expr: sqrt_c_expr = ksqrt(2) => sqrt(c)=ksqrt(2) => c=2*k^2
k = sp.simplify(sp.factor(sp.sqrt(2)b_sym_val / sp.sqrt(2))) # k = b_sym_val k = b_sym_val c_int = sp.simplify(2k**2) print("c_int =", c_int)
Now compute abc/pi
a = area b_val = sp.simplify(b_int) c_val = sp.simplify(c_int) abc_over_pi = sp.simplify(ab_valc_val/sp.pi) print("abc/pi =", abc_over_pi) [/PYTHON]
[THOUGHT] From the Python results: (a = \frac{9\pi}{2}), slope (= -2 + \sqrt{2}), so (b=-2) and (c=2). Then [ \frac{abc}{\pi} = \frac{\left(\frac{9\pi}{2}\right)(-2)(2)}{\pi} = -18. ] [/THOUGHT] \boxed{-18}