Describe the two possible ways to use the angle of depression that is outside a right triangle?

You can use the virtue of similar triangles to get the complement angle on the opposite side which is the object or you can use the depression angle to get the complement angle forming a 90 degree angle vertical to the ground. This follows that for any angle x being the angle of depression, its complement angle will always sum up to 90. This will be a handy trick once you will be introduced to courses that involves primarily using trigonometry.