Question 133
A vertical mast $AB$ high $1\,m$ is illuminated by rays of the sun and forms shadows in the horizontal plane of lengths: $1$, $2$ and $3$ meters at three different times. Prove that the sum of the angles of incidence of the rays in these three moments forms a right angle, that is, $$
\angle ACD + \angle AEB + \angle ADB = 90^\circ
$$
\angle ACD + \angle AEB + \angle ADB = 90^\circ
$$