Let AB denote the height of the tower. Let BC denote the distance from the base of the tower. Then triangle ABC is a right angled triangle, right angled at B which is the base of the tower.
Applying trigonometric identities,we get tan C = tan 45° =
AB
BC
=
H
20
tan45°=
H
20
H=20tan45° =20 Hence the height of the tower is 20 meters