The ratio of the length of a tree and its shadow is 1:1/.The angle of sun's elevation is

Let ∠ACB be the angular elevation of the sun.

Let AB be the rod and BC be its shadow.

Now AB/BC = 1/1 , SO AB = BC

In triangle ABC,

tan ∠ACB = AB/BC = AB/ AB

So, tan ∠ACB = 1

 ⇒ tan ∠ACB = tan 45°

 ⇒ ∠ACB =  45°