the angle of elevation 23°30' which is the same as the angle from the base of the boulder to the top of the tree (alterne /intern)
Now we have a right triangle with an angle of 20°30' facing the tree & the horizontal leg of this triangle is 54 m.
Let x be the height of the tree
Then tan(23°30') =x/54 & tan(23°30') = 0.435
0.435 = x/54 ==> x = 0.435 x 54 ==> x = 23.49 m or 23.5 m
