Question

The diagram shows a regular pentagon, ABCDE, a regular octagon, ABFGHIJK, and an isosceles triangle, BCF. Work out the angle x

Answer 1

Answer:

x is 31.5°

Step-by-step explanation:

Here, we have each interior angle of a regular octagon = 135°

Each interior angle of a regular pentagon = 108°

Therefore, 135° + 108° + ∡B = 360°

Hence, ∡B = 360° - (135° + 108°) = 117°

Since, AB = BC = BF ( sides of a regular polygons (octagon and pentagon))

Hence, ΔCBF is an isosceles triangle and ∡x = ∡CFB  from which we have;

∡x + ∡CFB + 117° = 180°

∴  ∡x + ∡CFB = 180° - 117° = 63°

Hence, ∡x = 63° - ∡CFB = 63° - ∡x which gives

2·∡x = 63°

Hence, ∡x = 63°/2 = 31.5°

∡x = 31.5°.