英文四邊形數學題(15分)

1.
PQ//SR (prop. of trapezium)
125 degrees + a = 180 degrees (int. angles, PQ//SR)
a = 180 degrees - 125 degrees
a = 55 degrees

2.
WX//ZY (prop. of trapezium)
2x + 50 degrees = 180 degrees (int. ∠s, WX//ZY)
2x = 180 degrees - 50 degrees
x = 130 degrees / 2
x = 65 degrees

y + 90 degrees = 180 degrees (int. ∠s, WX//ZY)
y = 180 degrees - 90 degrees
y = 90 degrees

PS. 打唔到角度既符號, 所以用degrees代替

Draw a vertical line PM such that PM⊥RS

Then Angle QPM=Angle SMP=90

Angle SPM=125-90=35

So

a

=180-Angle SMP- Angle SPM

=180-90-35

=90-35

=55

(b)

y=90

Draw a vertical line XM such that XM⊥YZ

Angle WXM=90

Angle YXM=180-90-50=40

Angle X=90+40=130

So x=130/2=65