We have to use the tangent of angle 40 to find the height of the tower.
[tex]\text{tan(angle) = }\frac{opposite\text{ side}}{\text{adjacent side}}[/tex]The adjacent side is 20m, and the angle is 40 degrees, then
[tex]\tan (40)\text{ = }\frac{height\text{ of the tower}}{20m}[/tex][tex]\text{height = 20m }\cdot\text{ tan(40) = 20m }\cdot0.84\text{ = }16.8m[/tex]Therefore, the height of the tower is 16.8m
