Formula to calculate a length to a point on hypotenuse according to given angle I have a right triangle:


*

*Height: y (value over 0)

*Width: y (value over 0)

*Angle: α (degrees, value between 0-90)



I need to find out the formula to count the length of x.

Yes, it's possible. The law of sines used on the lower triangle (the one spanned by $\alpha$) say that
$$
\frac{\sin(135^\circ - \alpha)}{1} = \frac{\sin \alpha}{x}
$$
where $135^\circ - \alpha$ is the measure of the top angle of the triangle (the lower left angle has measure $45^\circ$). So we have
$$
x = \frac{\sin{\alpha}}{\sin(135^\circ - \alpha)}
$$
