Math Problem Statement

A sphere is inscribed in a cone of radius 5 and height 12. Find the radius of the sphere.

Solution

To find the radius of the sphere inscribed in a cone, we need to use geometric relationships between the dimensions of the cone and the inscribed sphere. Let the radius of the cone’s base be R=5R = 5, the height of the cone be h=12h = 12, and the radius of the inscribed sphere be rr.

We can use the following formula for the radius of a sphere inscribed in a cone:

r=RhR2+h2+Rr = \frac{R \cdot h}{\sqrt{R^2 + h^2} + R}

Step-by-Step Solution:

  1. Substitute the given values: R=5,h=12R = 5, \quad h = 12

  2. Calculate R2+h2R^2 + h^2: R2+h2=52+122=25+144=169R^2 + h^2 = 5^2 + 12^2 = 25 + 144 = 169

  3. Take the square root of R2+h2R^2 + h^2: 169=13\sqrt{169} = 13

  4. Substitute into the formula: r=51213+5=6018=103r = \frac{5 \cdot 12}{13 + 5} = \frac{60}{18} = \frac{10}{3}

Thus, the radius of the inscribed sphere is:

r=1033.33units.r = \frac{10}{3} \approx 3.33 \, \text{units}.

Would you like more details or have any questions?

Here are 5 related questions:

  1. How do you derive the formula for the radius of an inscribed sphere?
  2. What is the volume of the cone in this problem?
  3. How does the radius of an inscribed sphere change with the cone’s height?
  4. Can the inscribed sphere's volume be calculated using its radius?
  5. How would the problem change if the cone had a slant height instead of a vertical height?

Tip: When solving geometric problems with inscribed shapes, understanding the relationship between the dimensions of the larger figure and the inscribed shape can help simplify the problem.

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Math Problem Analysis

Mathematical Concepts

Geometry
Inscribed Shapes
Right Circular Cone
Sphere

Formulas

r = (R * h) / (sqrt(R^2 + h^2) + R)

Theorems

Pythagorean Theorem (for deriving the slant height)

Suitable Grade Level

Grades 9-12