What is the minimum number of measurements required to determine the height or distance or angle of elevation?

What is the minimum distance (in metres ) required to hear an echo ?

To construct a unique rectangle, the minimum number of measurements required is

To construct a unique parallelogram, the minimum number of measurements required is

If the distance of a point from the tower is equal to the height of the tower , then find the angle of elevation of the top of the tower from that point .

If the distance of a point from the tower is equal to the height of the tower , then find the angle of elevation of the top of the tower from that point .

The angle of elevation of the top of a tower from the bottom of a building is twice that from its top. What is the height of the building, if the height of the tower is 75 m and the angle of elevation of the top of the tower from the bottom of the building is 60^@ ?

The angle of elevation of the top of a tower from the bottom of a building is twice that from its top. What is the height of the building if the height of the tower is 75 m and the angle of elevation of the top of the tower from the bottom of the building is 60^(@) ?