For 10 points
Find the General Solution of this Equation:
(x*sin^2(y/x) + y)dx - xdy = 0
Find the General Solution of this Equation:
(x*sin^2(y/x) + y)dx - xdy = 0
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x * sin(y/x)^2 * dx + y * dx - x * dy = 0
x * sin(y/x)^2 * dx = x * dy - y * dx
(x/x^2) * sin(y/x)^2 * dx = (x * dy - y * dx) / x^2
dx / x = csc(y/x)^2 * (x * dy - y * dx) / x^2
y/x = t
(x * dy - y * dx) / x^2 = dt
dx / x = csc(t)^2 * dt
Now integrate
ln|x| = -cot(t) + C
ln|x| = -cot(y/x) + C
cot(y/x) = C - ln|x|
y/x = arccot(C - ln|x|)
y = x * arccot(C - ln|x|)
x * sin(y/x)^2 * dx = x * dy - y * dx
(x/x^2) * sin(y/x)^2 * dx = (x * dy - y * dx) / x^2
dx / x = csc(y/x)^2 * (x * dy - y * dx) / x^2
y/x = t
(x * dy - y * dx) / x^2 = dt
dx / x = csc(t)^2 * dt
Now integrate
ln|x| = -cot(t) + C
ln|x| = -cot(y/x) + C
cot(y/x) = C - ln|x|
y/x = arccot(C - ln|x|)
y = x * arccot(C - ln|x|)
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(x*sin^2(y/x) + y) dx = x dy
u = y/x
u + xu' = y'
(x*sin^2(u) + ux) = xu + x^2u'
x*sin^2(u) = x^2(du/dx)
1/x dx = csc^2(u) du
Integrating both sides:
ln|x| + C = -cot(u)
u = tan(-1/(ln|x| + C))
y = x*tan(-1/(ln|x| + C))
u = y/x
u + xu' = y'
(x*sin^2(u) + ux) = xu + x^2u'
x*sin^2(u) = x^2(du/dx)
1/x dx = csc^2(u) du
Integrating both sides:
ln|x| + C = -cot(u)
u = tan(-1/(ln|x| + C))
y = x*tan(-1/(ln|x| + C))