f.2 maths 1題20分

因為我讀書o既時候係讀中文o既,所以我唔識英文係點答~
不過希望都可以幫到你~
仲有我唔記得晒d定理個名,就算記得都係中文,記得自己加返,唔係冇分ga^^~
(留意我o係呢度打唔到(度)既符號,你都要自己加返)

設x為多邊形其中一個外角
x+(x+100)=180
2x+=80
x=40

設y is the number of sides of this polygon
xy=360(好似係多邊形外角和)
y=9

so the number of sides of this polygon is 9~

仲有咩唔識可以隨時問我^^

let n= no. of sides and x = each size of ext. angle
then 180- x = each size of int . angle
hence (180-x) - x = 100(angle on a st. line)
180 - 2x = 100
80 = 2x
x = 40

since 40 n = 360 (angle sum of ext angle)
n = 9