Given the equation:
$$\frac{d}{d x} y{\left(x \right)} = \sin{\left(y{\left(x \right)} \right)}$$
This differential equation has the form:
$$f_1(x)\ g_1(y)\ y' = f_2(x)\ g_2(y)$$
where
$$f_{1}{\left(x \right)} = 1$$
$$g_{1}{\left(y \right)} = 1$$
$$f_{2}{\left(x \right)} = 1$$
$$g_{2}{\left(y \right)} = \sin{\left(y{\left(x \right)} \right)}$$
We give the equation to the form:
$$\frac{g_1(y)}{g_2(y)}\ y'= \frac{f_2(x)}{f_1(x)}$$
Divide both parts of the equation by $g_{2}{\left(y{\left(x \right)} \right)}$
$$\sin{\left(y{\left(x \right)} \right)}$$
we get
$$\frac{\frac{d}{d x} y{\left(x \right)}}{\sin{\left(y{\left(x \right)} \right)}} = 1$$
We separated the variables x and y.
Now, multiply the both equation sides by dx,
then the equation will be the
$$\frac{dx \frac{d}{d x} y{\left(x \right)}}{\sin{\left(y{\left(x \right)} \right)}} = dx$$
or
$$\frac{dy}{\sin{\left(y{\left(x \right)} \right)}} = dx$$
Take the integrals from the both equation sides:
- the integral of the left side by y,
- the integral of the right side by x.
$$\int \frac{1}{\sin{\left(y \right)}}\, dy = \int 1\, dx$$
Detailed solution of the integral with yDetailed solution of the integral with xTake this integrals
$$\frac{\log{\left(\cos{\left(y \right)} - 1 \right)}}{2} - \frac{\log{\left(\cos{\left(y \right)} + 1 \right)}}{2} = Const + x$$
Detailed solution of the equationWe get the simple equation with the unknown variable y.
(Const - it is a constant)
Solution is:
$$y_{1} = y{\left(x \right)} = - \operatorname{asin}{\left(\frac{1}{\tanh{\left(C_{1} + x \right)}} \right)} + \frac{3 \pi}{2}$$
$$y_{2} = y{\left(x \right)} = \operatorname{acos}{\left(- \frac{1}{\tanh{\left(C_{1} + x \right)}} \right)}$$