In the figure above, LM is a lighthouse from the top of which John vie...
Steps 1 & 2: Understand Question and Draw Inferences
In this question, the angle between the horizontal and John’s line of sight when he looks at object A from point L is given to be 60o.
This means, in right triangle LMA, Angle MAL = 60°
By using the Angle Sum Property, we can find that Angle ALM = 30°
Triangle AML is a 30° -60° -90° triangle. In such a triangle, the sides opposite to the angles 30°, 60°, and 90° respectively are in the ratio 1 : √3 : 2
That is, MA: LM : AL = 1 : √3 : 2
Now, we need to find the distance between the bottom of the lighthouse and object A. That is, we need to find the length of MA.
Let the length of MA be x feet.
Thus,LM=3√x
And, AL=2x
John then moves downstairs to the middle of the lighthouse. Let the middle point be C.
So, MC=LC=√3x/2
Let the angle of depression from Point C to object A be y°
By Applying Pythagoras Theorem in right triangle AMC, we get:
AC2=MC2+AM2
Thus, we have expressed all sides of the right triangles AML and AMC in terms of x. If we know any of these sides, we will be able to find the value of x.
Step 3: Analyze Statement 1
The distance between the top of the lighthouse and object A is 80 feet
AL=80
This means
2x=80
x=40
Thus, Statement 1 alone is sufficient.
Step 4: Analyze Statement 2
The distance between the middle of the lighthouse and object A is 20√7 feet
AC=20√7
This means,
x=40
Thus, Statement 2 alone is sufficient.
Step 5: Analyze Both Statements Together (if needed)
There is no need to analyze further as both statements (1) and (2) are sufficient.