Depression

A triangle in which one of the interior angles is 90°

is the angle from the horizontal to the line of sight of the observer to the object below.

opposite/hypotenuse

opposite/adjacent

is an imaginary line that connects the eye of an observer to the object being observed.

defined as the values of all the trigonometric functions based on the value of the ratio of sides in a right-angled triangle.

is the angle from the horizontal to the line of sight of the observer to the object above.

longest part of a right triangle

adjacent/hypotenuse