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POLYGONS

  • ALL CLOSED SHAPES WITH SIDES ARE CALLED POLYGONS
  • CATEGORISED IN 2; REGULAR POLYGONS & NON REGULAR POLYGONS
  • RUPABENTUK MESTI BERTUTUP DAN MEMPUNYAI SISI
  • DIBAHAGI DALAM 2 KATEGORI IAITU POLIGON BIASA DAN POLIGON BUKAN BIASA

REGULAR POLYGONS

  • ALL SIDES ARE EQUAL IN TERM LENGTH
  • ALL ANGLES (INTERIOR & EXTERIOR) ARE EQUAL
  • FORMULA FOR TOTAL INTERIOR ANGLES = (n-2) x 180º WHERE n REPRESENT NUMBER OF SIDES
  • FORMULA FOR EACH INTERIOR ANGLE = TOTAL INTERIOR ANGLE ÷ n
  • TOTAL EXTERIOR ANGLES = 360º
  • AN EXTERIOR ANGLE AND AN INTERIOR ANGLE MUST FORM A STRAIGHT LINE WITH A TOTAL DEGREES = 180º
  • SEMUA SISI MESTI MEMPUNYAI PANJANG YANG SAMA
  • SEMUA DARJAH (DALAMAN & LUARAN) MESTI SAMA
  • FORMULA UNTUK MENGIRA JUMLAH DARJAH DALAMAN = (n-2) x 180º DIMANA n MEMBAWA MAKSUD BILANGAN SISI
  • FORMULA UNTUK MENDAPAT SETIAP DARJAH DALAMAN = JUMLAH DARJAH DALAMAN ÷ n  
  • JUMLAH DARJAH LUARAN360º
  • DARJAH LUARAN DAN DARJAH DALAMAN MESTI MEMBENTUK SATU GARIS LURUS YANG MEMBAWA JUMLAH DARJAH =  180º
SHAPE OF REGULAR POLYGONS

NON REGULAR POLYGONS

  • SIDES ARE NOT TOTALLY EQUAL IN TERM OF LENGTH
  • ALL ANGLES (INTERIOR & EXTERIOR) NOT TOTALLY THE SAME
  • FORMULA FOR TOTAL INTERIOR ANGLES = (n-2) x 180º WHERE n REPRESENT NUMBER OF SIDES
  • NO PARTICULAR FORMULA TO CALCULATE THE DEGREE FOR EACH ANGLE
  • TOTAL EXTERIOR ANGLES = 360º
  • AN EXTERIOR ANGLE AND AN INTERIOR ANGLE MUST FORM A STRAIGHT LINE WITH A TOTAL DEGREES = 180º
  • SISI TIDAK MEMPUNYAI PANJANG YANG SAMA
  • SEMUA DARJAH (DALAMAN & LUARAN) TIDAK SAMA
  • FORMULA UNTUK MENGIRA JUMLAH DARJAH DALAMAN = (n-2) x 180º DIMANA n MEMBAWA MAKSUD BILANGAN SISI
  • TIADA FORMULA UNTUK MENDAPAT SETIAP DARJAH DALAMAN
  • JUMLAH DARJAH LUARAN = 360º
  • DARJAH LUARAN DAN DARJAH DALAMAN MESTI MEMBENTUK SATU GARIS LURUS YANG MEMBAWA JUMLAH DARJAH =  180º

 SHAPE OF NON REGULAR POLYGONS
EXAMPLE
Based on the given shape of regular polygon in the diagram below , calculate the  value for a and b

Since this is a regular polygon, then all the sides and angles must have the same value.

First we need to find the value of a, but to do so we must be able to find the total value of the interior angles. By using the given formula of (n-2) x 180º and knowing n = 6 sides; therefore

(6 – 2) x 180º = 720º

720º ÷ 6 = 120º ( each interior angle = 120º )

As such, a = 120º

We know that an interior angle + an exterior angle = 180º ( forming a straight line )

Therefore, to find b = 180º – 120º = 60º