Question

There is a lightning rod on top of a building. From a location 500 feet from the base of the building, the angle of elevation to the top of the building Is measured to be 36 degrees. From the same location, the angle of elevation to the top of the lightning rod is measured to be 38 degrees. Find the height of the lightning rod. Round to the nearest foot.

Answer 1

Hello!

The answer is:

The height of the  lightning rod is 27.4 feet.

Why?

To solve the problem, we need to use the given information about the two points of observation, since both are related (both finish and start at the same horizontal distance) we need to write to equations in order to establish a relationship.

So, writing the equations we have:

We know that the angle of elevation from the base of the buildings is 36°

Also, we know that from the same location, the angle of elevation to the top of the lightning rod is 38°.

Using the information we have:

To the top of the building:

$tan(\alpha )=\frac{DistanceToTheTopOfTheBuilding}{BuildingBase}\\\\tan(36\°)=\frac{DistanceToTheTopOfTheBuilding}{BuildingBase}$

To the top of the lightning rod:

$tan(\alpha )=\frac{DistanceToTheTopOfTheLightningRod}{BuildingBase}\\\\tan(38\°)=\frac{DistanceToTheTopOfTheLightningRod}{BuildingBase}$

Now, isolating we have:

$tan(36\°)=\frac{DistanceToTheTopOfTheBuilding}{BuildingBase}\\\\DistanceToTheTopOfTheBuilding=tan(36\°)*BuildingBase \\\\DistanceToTheTopOfTheBuilding=tan(36\°)*500feet=363.27feet$

Also, we have that:

$tan(38\°)=\frac{DistanceToTheTopOfTheLightningRod}{BuildingBase}\\\\DistanceToTheTopOfTheLightningRod=tan(38\°)*BuildingBase\\\\DistanceToTheTopOfTheLightningRod=tan(38\°)*500feet=390.64feet$

Therefore, if we want to calculate the height of the lightning rod, we need to do the following:

Let "x" the distance to the top of the building and "y" the distance to the top of the lightning rod, so:

$LightningRodHeight=y-x=390.64feet-363.27feet=27.37feet$

Rounding to the nearest foot, we have:

$LightningRodHeight=y-x=390.64feet-363.27feet=27.37feet=27.4feet$

Hence, the answer is:

The height of the lightning rod is 27.4 feet.

Have a nice day!