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AB, BC, and CD are the three consecutive sides of a regular polygon. If BAC = 15°; Find: i. Each interior angle of the polygon. ii. Each exterior angle of the polygon. - Mathematics

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Question

AB, BC, and CD are the three consecutive sides of a regular polygon. If BAC = 15°;

Find:

  1. Each interior angle of the polygon.
  2. Each exterior angle of the polygon.
  3. The number of sides of the polygon.
Sum

Solution

(i) Let each angle of measure x degree.

Therefore, the measure of each angle will be:

x = 180° - 2 × 15° = 150°

(ii) Let each angle of measure x degree.

Therefore, the measure of each exterior angle will be :

x = 180° - 150° = 30°

(iii) Let the number of each side is n.

Now we can write

n.150° = (2n - 4) × 90°

180°n - 150°n = 360°

30°n = 360°

n = 12

Thus, the number of sides is 12.

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Chapter 14: Rectilinear Figures [Quadrilaterals: Parallelogram, Rectangle, Rhombus, Square and Trapezium] - Exercise 14 (A) [Page 169]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 14 Rectilinear Figures [Quadrilaterals: Parallelogram, Rectangle, Rhombus, Square and Trapezium]
Exercise 14 (A) | Q 8 | Page 169
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