 
This type of question first appears in grade 10 math as an example of a more difficult trig problem:"You measure the angle to the top of a building to be 60°. After moving 95 metres closer to the building, you measure the angle again, to be 70°. How tall is the building?" Let's look at three ways to solve this problem. Double Tan Solution: This is the Math 10 method, using tan and some fancy algebra. 
We assume that the building is at a 90° angle with the ground, since Math 10 only deals with right angle trigonometry. We'll also need to introduce another variable 'a' for the distance to the building from your second angle measurement. So the base of the large triangle is 95 + a. Start by finding the tan of both angles:   This gives us an answer of approximately 445 m for the height of the building. Let's look at a second method, using a formula >>> |