Math Problem Statement

Viewed from Earth, the Moon’s angular size is about 0.52 degrees. Assume the distance from the Earth to the Moon is 380, 000 kilometers. What is the diameter of the moon in miles? (Hint: remember that units of size and distance must match.)

Solution

To solve this problem, we can use the formula for angular size, which relates the diameter of an object to its distance from the observer:

Angular size=Diameter of the objectDistance to the object\text{Angular size} = \frac{\text{Diameter of the object}}{\text{Distance to the object}}

First, we'll convert the angular size from degrees to radians. The relationship between degrees and radians is given by:

1 degree=π180 radians1 \text{ degree} = \frac{\pi}{180} \text{ radians}

So, the angular size in radians is:

Angular size in radians=0.52×π180\text{Angular size in radians} = 0.52 \times \frac{\pi}{180}

Next, rearrange the formula for angular size to solve for the diameter of the Moon:

Diameter of the Moon=Angular size in radians×Distance to the Moon\text{Diameter of the Moon} = \text{Angular size in radians} \times \text{Distance to the Moon}

Finally, we'll convert the distance from kilometers to miles by using the conversion factor:

1 kilometer=0.621371 miles1 \text{ kilometer} = 0.621371 \text{ miles}

Let's calculate this step by step.The diameter of the Moon is approximately 2,143 miles.

Would you like more details or have any other questions? Here are some related questions for further exploration:

  1. How does the angular size of the Moon change when it is closer to the Earth?
  2. What is the formula for converting angular size from degrees to radians?
  3. How does the distance to the Moon vary over time, and how does that affect its angular size?
  4. How can you calculate the distance to an object if you know its angular size and actual diameter?
  5. What is the significance of knowing the Moon's diameter in astronomy?

Tip: Understanding the relationship between angular size and distance is crucial for calculating the sizes of celestial objects seen from Earth.

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Math Problem Analysis

Mathematical Concepts

Geometry
Trigonometry
Unit Conversion

Formulas

Angular size formula
Conversion from degrees to radians
Distance conversion from kilometers to miles

Theorems

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Suitable Grade Level

Grades 9-12