Video narration
How can you find the height of a tall tree without climbing it or measuring it directly? Stand a known distance from the tree and look at its top. The ground, tree, and line of sight form a right triangle. The angle measured from the horizontal is the angle of elevation. Now the height is no longer unreachable: it is the opposite side of a triangle you can calculate. Suppose you stand 10 metres away and measure 45 degrees. Tangent links the opposite height to the adjacent distance: tangent of 45 degrees equals height divided by 10. Because tangent of 45 degrees is 1, the height above your eyes is 10 metres. Add your eye height for the tree's total height. The same triangle can find distance when the height and angle are known. So how can you measure a tree without touching it? Trigonometry links a viewing angle and one measured distance in a right triangle, making the tree's height calculable.