Math Problem Statement

The shape below is part of a football that has been unstitched and laid flat. It is made up of one regular pentagon and two regular hexagons. What is the size of angle x?

Solution

To solve for the angle xx in the image, we need to consider the geometrical properties of the shapes provided (a regular pentagon and two regular hexagons).

Step 1: Angles in a Regular Pentagon and Hexagon

  • A regular pentagon has interior angles of 108108^\circ because the formula for the interior angle of any regular polygon is given by: Interior angle=(n2)×180n\text{Interior angle} = \frac{(n-2) \times 180^\circ}{n} where nn is the number of sides. For a pentagon, n=5n = 5: (52)×1805=3×1805=108\frac{(5-2) \times 180^\circ}{5} = \frac{3 \times 180^\circ}{5} = 108^\circ

  • A regular hexagon has interior angles of 120120^\circ, derived similarly for n=6n = 6: (62)×1806=4×1806=120\frac{(6-2) \times 180^\circ}{6} = \frac{4 \times 180^\circ}{6} = 120^\circ

Step 2: Understanding Angle xx

The image shows two hexagons and one pentagon adjacent to each other, with angle xx between the hexagon and the pentagon. The angle at that vertex is the external angle formed by the intersection of these polygons.

The key observation is that the external angles around a point sum to 360360^\circ. The external angle of a polygon is 180180^\circ - interior angle. Thus:

  • The external angle of the pentagon is: 180108=72180^\circ - 108^\circ = 72^\circ
  • The external angle of each hexagon is: 180120=60180^\circ - 120^\circ = 60^\circ

Step 3: Solving for xx

Since the external angles must sum to 360360^\circ, we can calculate xx as the remaining angle at the vertex. Adding up the external angles: 60(hexagon)+60(other hexagon)+72(pentagon)+x=36060^\circ (\text{hexagon}) + 60^\circ (\text{other hexagon}) + 72^\circ (\text{pentagon}) + x = 360^\circ 60+60+72+x=36060^\circ + 60^\circ + 72^\circ + x = 360^\circ 192+x=360192^\circ + x = 360^\circ x=360192=168x = 360^\circ - 192^\circ = 168^\circ

Thus, the size of angle xx is 168168^\circ.

Would you like more details on any step or have any questions?

Related Questions:

  1. How is the formula for the interior angle of a regular polygon derived?
  2. What are the external angles of an octagon?
  3. If a triangle and a pentagon were placed together, how would you find the angle between them?
  4. What would the angle xx be if one of the hexagons were replaced with a square?
  5. Can you generalize a formula to find xx for any combination of polygons at a vertex?

Tip:

For polygons, always remember that the sum of the external angles around a point is always 360360^\circ, regardless of the shapes!

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Math Problem Analysis

Mathematical Concepts

Geometry
Polygons
Angles

Formulas

Interior angle of a polygon = ((n-2) * 180) / n
External angle of a polygon = 180 - Interior angle
Sum of external angles at a point = 360 degrees

Theorems

Sum of external angles around a point

Suitable Grade Level

Grades 9-12