 This is a real life problem my husband came up with about a year ago at our cabin. We're building a cabin in northern Minnesota and he said I wonder how high up off the water we are. And I said oh I can do this with trigonometry. We know that we are 105 feet back from the water's edge. We had to know that in order to get our building permit. And I went up to the second story of our cabin and held a carpenter's compass to my eye with a level on top so I knew it was horizontal and sited down to the water and found out that it was 25 degrees from horizontal angle of depression down to the water. Because I know that horizontal at the second story window and horizontal at the water's edge are parallel I know that if this is a 25 degree angle it is also a 25 degree angle down here because remember the horizontals are parallel so this 25 degrees is an alternate interior angle to this angle here so I can make that angle be 25 degrees. From this 25 degrees I want to know I already know the 105 degree set back sorry the 105 foot set back and I wish I knew this height from the water up to the second story window because this height distance is opposite the 25 and the 105 feet the horizontal is adjacent to the 25 I'm going to use tangent. So tangent of 25 degrees equals opposite over adjacent. So tangent of 25 degrees is x I'm going to multiply both sides of the equation by 105 to start to solve and I get 105 times tangent of 25 equals the distance I'm trying to calculate and when I punch that into my calculator I get 48.96 so the distance up to the second window of the cabin is approximately 49 feet or 50 feet if I want to impress my friends and neighbors. So that's how high up my cabin is off of the surface of the lake good to know.